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In this study, we have examined whether the suppression of raised plasma FSH concentrations at pro-oestrus and/or oestrus by porcine follicular fluid (PFF) affected the development of follicles for ovulation in the next cycle. Adult, 4-day-cyclic rats were injected with PFF or pig serum at various hours of pro-oestrus and oestrus. Plasma FSH levels were suppressed following PFF treatment at any time of pro-oestrus and oestrus. Furthermore, this suppression was always followed by a 'rebound' increase in plasma FSH. In contrast, plasma LH concentrations were unaffected by PFF treatment and neither gonadotrophin was altered by treatment with pig serum.
When rats treated with PFF or pig serum were allowed to complete one additional cycle, plasma LH and FSH concentrations at the pro-oestrus and oestrus after treatment were not significantly different among groups regardless of treatment or time of treatment. All ovaries of rats treated with PFF or pig serum on the next pro-oestrus morning before ovulation were histologically similar. Furthermore, all animals ovulated a normal complement of ova at the next oestrus regardless of whether preovulatory, secondary or both increases of plasma FSH had been blocked by PFF treatment during the previous cycle. However, in animals given PFF during the preceding cycle, plasma oestradiol and progesterone concentrations were significantly altered on the morning and afternoon of pro-oestrus respectively.
These results suggest that increased plasma FSH concentrations at pro-oestrus and oestrus may not be essential for folliculogenesis and ovulation in the subsequent cycle. Alternatively, the 'rebound' of FSH on day 1 of dioestrus after the suppression of both phases of FSH secretion at pro-oestrus and oestrus may be sufficient to provide ovulatory follicles for the next pro-oestrous day.
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Relaxin reference preparations NIH-R-P1 and Warner Lambert W1164-3, and purified relaxin peptides, CM-a′, CM-a and CM-B, were assayed in the mouse interpubic ligament and rat uterine inhibition bioassays. There was evidence that CM-a and CM-B would bind to glass and significant apparent increases in potency in the case of these two peptides alone resulted from the use of silicone-coated glassware. Using treated glassware, CM-a′, CM-a and CM-B were equipotent in the mouse interpubic ligament bioassay with potencies relative to NIH-R-P1 of 3·97-, 4·85- and 3·64-fold respectively. In the rat uterine inhibition bioassay only W1164-3 and CM-a′ gave dose-response curves which were parallel to NIH-R-P1. In this bioassay, potencies relative to NIH-R-P1 for W1164-3 and CM-a' were 0·35-and 19·6-fold respectively.
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ABSTRACT
Peptide YY (PYY), a thirty-six amino acid intestinal hormonal peptide with a tyrosine residue at each end (hence YY as Y represents tyrosine in the new peptide nomenclature), was found throughout the gastrointestinal tract of the pig. Concentrations were very low in the foregut (antrum, 3·4 ± 0·3 pmol/g; duodenum, 1·1 ± 1·5 pmol/g), higher in the distal small intestine (ileum, 100 ± 13 pmol/g) and very high in the large bowel (descending colon, 270 ± 45 pmol/g).
Peptide YY was found to circulate in plasma and concentrations rose substantially in response to eating (fasting, 138 ± 15 pmol/l; postprandial, 263 ± 21 pmol/l; P<0·001). There was a small but significant portal/arterial gradient in postprandial PYY levels.
More than 90% of the immunoreactive PYY in gut extracts eluted, on gel permeation chromatography, in an identical position to pure PYY standard, but small amounts of higher molecular weight material, possibly precursors, were detected. In contrast, plasma from fasting pigs contained a large proportion (60–70%) of these large molecular forms. These findings suggest that the putative pro-PYY may be cleared more slowly from the circulation than the 36 amino acid hormonal peptide.
The high concentrations of immunoreactive PYY in the circulation of the young pig may reflect a species difference between pig and man or may indicate an important role for PYY in the developing animal.
J. Endocr. (1987) 113, 11–14
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The surgically isolated thyroid gland in the pig has been shown to secrete thyrocalcitonin (TC) when perfused with an artificial medium, hypercalcaemic with respect to ionized calcium concentration (Care & Gitelman, 1968). Therefore, hypophysial hormones must not be essential for the release of at least some TC stimulated by hypercalcaemia. The present work was designed to evaluate quantitatively the effect of previous hypophysectomy on the rate of secretion of TC in response to a given degree of hypercalcaemia.
In preliminary experiments, a pair of litter-mate male piglets, 19 days old, was selected and one was hypophysectomized by an adaptation of the method of Liggins, Kennedy & Holm (1967). At autopsy, hypophysectomy was confirmed by visual examination of the sella turcica. Nine days after operation, the thyroid was isolated in situ and perfused with hypercalcaemic blood (6·7 m-equiv.Ca/1.) for 2 hr. according to the method of Care (1965). The thyroid of
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College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, People’s Republic of China
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College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, People’s Republic of China
Joint International Research Laboratory of Agriculture and Agri-Product Safety, The Ministry of Education of China, Yangzhou University, Yangzhou, Jiangsu, People’s Republic of China
Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, Jiangsu, People’s Republic of China
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inhibitors were purchased from MCE (MedChemExpress, Shanghai, China). To assay the effects of NE on miR-7 level and the synthesis and secretion of FSH and LH in pituitary, the primary cultured porcine anterior pituitary cells were treated with 10 −7 mol
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ABSTRACT
The ontogeny of fetal lung glucocorticoid receptors and their regulation by the fetal pituitary, adrenal and thyroid gland during lung maturation were investigated. Sites with a specificity typical of glucocorticoid receptors were detectable in lung cytosol, with the order of potency of steroids being dexamethasone > cortisol > corticosterone > 11- -deoxycorticosterone > progesterone > 17α-hydroxyprogesterone > oestradiol -17β ≃ testosterone ≃ androstenedione ≃ oestrone. The binding affinity for [3H]dexamethasone was high (K d = 0·23–0·60 nmol/l) and showed an age-related decrease during the perinatal period when cortisol levels were high. After charcoal treatment of the cytosol, however, a decrease in binding affinity was not as clearly evident. The K d decreased following hypophysectomy of fetuses; thyroidectomy had no significant effect. The concentration of glucocorticoid receptors was high from day 82 to day 100 of gestation (1437 fmol/mg protein) and declined progressively to a lower value at term and following birth (660 fmol/mg protein). Hypophysectomy, but not thyroidectomy, prevented the age-related decline in receptor concentration. Lung glycogen content declined with fetal ageing in association with increases in plasma concentrations of cortisol and thyroxine and with changes in K d and B max, but appeared to be more closely associated with concentrations of thyroxine. Hypophysectomy of fetuses decreased concentrations of both cortisol and thyroxine and prevented the depletion of lung glycogen content. Preliminary results from thyroidectomized fetuses showed decreases in plasma thyroxine and lung glycogen content compared with day-82 fetuses. Plasma cortisol levels, however, were consistent with a fetal age of 113 days. The effects of thyroxine on lung glycogen depletion, therefore, appear to occur, at least in part, through a pathway independent of glucocorticoid receptors.
Journal of Endocrinology (1990) 127, 341–349
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ABSTRACT
Homogenates of pig corpora lutea contained specific, high-affinity receptors for ovine prolactin (oPRL) and human GH (hGH). Specific hormone binding was enhanced by divalent metal ions, but only when included in the binding reaction. Divalent metal ions did not act by increasing the recovery of bound hormone by low-speed centrifugation, but appeared to promote the formation of a more stable hormone– receptor complex. Both oPRL and hGH tracers were bound in similar amounts and with similar affinities by pig luteal homogenates and the concentrations of either unlabelled hormone required to displace specific binding of either tracer by 50% were identical.
In contrast, 125I-labelled oGH failed to bind to pig luteal homogenates and oGH competed poorly for hGH or oPRL binding. Only hormones with prolactin-like activity competed for 125I-labelled oPRL binding.
Specific prolactin binding was low in recently ovulated and early luteal phase corpora lutea, increased significantly in the mid-luteal phase and declined once more in the late luteal phase. Receptor concentrations increased with increasing gestational age.
J. Endocr. (1987) 113, 355–364
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Abstract
Porcine thyroid epithelial cells cultured as a monolayer with their apical membranes facing the medium are known to absorb Na+ and secrete Cl−. Two types of Na+ channels were found in cell-attached patches of apical membrane. A low conductance Na+ channel (conductance g=4 picosiemens (pS)) remained open for seconds and showed a high selectivity for Na+ compared with K+. In contrast, a high conductance Na+ channel (g=10 pS) flickered rapidly and had reduced selectivity. Both types of Na+ channel became more prevalent when the cells were exposed to Na+-free medium, though only the high conductance channel increased in prevalence on addition of prostaglandin E2, a stimulator of adenylate cyclase which increases Na+ absorption in this cultured epithelium. Two minority types of channel were also found: a non-selective small conductance cation channel which had been reported previously, and an intermediate conductance channel found only in Na+-free medium. It was concluded that passage of Na+ across the apical membrane of thyroid cells is mediated by typical epithelial Na+ channels, but that the two types of channel are differentially regulated.
Journal of Endocrinology (1996) 149, 101–108
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ABSTRACT
The formation of new capillaries, both in extraembryonic membranes and in the maternal endometrium, is an essential prerequisite for appropriate feto-maternal relationships throughout pregnancy. At present there is no indication of the nature of the uterine angiogenic stimulus. In-vitro, degradation products of hyaluronic acid, following its catalysis by hyaluronidase, have been shown to have angiogenic properties. In the current study, levels of hyaluronic acid in endometrial tissues and of hyaluronidase and hyaluronic acid in uterine flushings were measured during the oestrous cycle and early pregnancy.
The concentration of both hyaluronic acid and hyaluronidase in uterine flushings followed the growth and regression of the corpus luteum, in that basal levels detected on days 0 and 6 increased to peak concentrations on days 12 and 15. By day 18, levels of both hyaluronidase and hyaluronic acid had decreased in cyclic gilts, but remained increased in pregnant pigs. Tissue concentrations of hyaluronic acid were not affected by pregnancy or by the day of the oestrous cycle. In a subsequent experiment, four groups of gilts were ovariectomized on day 4 and thereafter received daily injections of corn oil, progesterone, oestrogen or a combination of oestrogen and progesterone. Hyaluronidase was undetectable in uterine flushings collected on day 15 from corn oil-and oestrogen-treated gilts, but present in similar amounts in uterine flushings from gilts treated with progesterone and progesterone plus oestrogen. Similarly, uterine fluid concentrations of hyaluronic acid were increased in progesterone- and progesterone plus oestrogen-treated gilts, but not in corn oil-or oestrogen-treated pigs. Tissue concentrations of hyaluronic acid were unaffected by steroid treatment.
These results indicate that progesterone stimulates secretion of hyaluronidase and hyaluronic acid; both substances believed to be associated with the presence of an angiogenic factor in the pig uterus, but there was no evidence of a synergistic interaction between progesterone and oestrogen.
Journal of Endocrinology (1990) 125, 15–19
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Biochemistry Laboratory, School of Biological Sciences, University of Sussex, Brighton BN1 9QG and *Armour Pharmaceutical Co. Ltd, Eastbourne, Sussex
(Received 3 May 1976)
Corticotrophin releasing hormone (CRH) has proved to be one of the more elusive hypothalamic releasing factors. It has resisted previous purification attempts and its structure is still unknown. Progress in purifying CRH appears to have been hampered both by the difficulties associated with its assay and by its molecular nature. Previous attempts to purify CRH using gel filtration have had only limited success (Dhariwal, Antunes-Rodriguez, Resser, Chowers & McCann, 1966; Chan, Schaal & Saffran, 1969). Recent reports on its characterization suggest that the hormone may exist in two forms of different molecular weight (Gillham, Jones, Hillhouse & Burden, 1975) or that a co-factor may be required for its action (Pearlmutter, Rapino & Saffran, 1975). We have recently subjected partially purified CRH to chromatography on Sephadex G-50 under
