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N. T. DAVIES
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K. A. MUNDAY
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B. J. PARSONS
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SUMMARY

A study was made of the effects of cyclic AMP, theophylline, cycloheximide, puromycin and actinomycin D on the stimulation by angiotensin of fluid transport by sacs of rat colon mucosa.

Cyclic AMP and theophylline, added together or separately, had no effect on fluid transport by colon sacs, suggesting that the stimulation of fluid transport after the application of angiotensin is not mediated through cyclic AMP. Cycloheximide and puromycin (used at concentrations which block colon protein synthesis by 50–90%) had no effect on fluid transport by control colon sacs, but completely blocked the stimulatory response of the colon to angiotensin. In contrast, actinomycin D (at a concentration which significantly inhibits RNA synthesis) did not affect fluid transport in control or angiotensin-stimulated colon sacs. The results are discussed in relation to the possibility that protein synthesis, at the stage of translation, is involved in the action of angiotensin on fluid transport by the colon.

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N. T. DAVIES
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K. A. MUNDAY
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B. J. PARSONS
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SUMMARY

Fluid transfer by isolated everted sacs of rat jejunum, ileum and intact colon prepared from adrenalectomized-nephrectomized rats 48 h after operation was reduced when compared with that of sacs prepared from untreated controls (P < 0·001). Angiotensin at 10−10 g/ml significantly (P < 0·01) stimulated fluid transfer by intestinal sacs prepared from the adrenalectomized-nephrectomized rats; all three regions of gut were equally sensitive.

Fluid transfer was similarly reduced in stripped colon sacs prepared from adrenalectomized-nephrectomized rats. Angiotensin had a dose-dependent biphasic action on fluid transfer by stripped colon sacs: low concentrations (10−11 and 10−12 g/ml) stimulated (P < 0·05), whilst high concentrations (10−9 and 10−8 g/ml) inhibited fluid transfer (P < 0·01). Histological examination of the colon preparations showed that the stripping procedure removed the ganglia, indicating that both angiotensin effects were due to direct action on the colon mucosa.

The significance of these results is discussed in relation to the role of angiotensin in the control of salt and fluid transport by the mammalian kidney and other epithelial tissues.

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JENNIFER E. BOLTON
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K. A. MUNDAY
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B. J. PARSONS
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A study has been made of the effects of protein synthesis inhibitors on the responses of rat jejunum in vivo to intravenous infusions of angiotensin. Actinomycin D, an inhibitor of the transcription stage of protein synthesis, was without effect on the stimulation of fluid transport which follows the infusion of low doses of angiotensin. Cycloheximide, an inhibitor of the translation stage of protein synthesis, blocked the stimulatory response to angiotensin, but was without effect on the inhibitory response to high doses of the hormone. It is concluded that low (physiological) doses of angiotensin stimulate fluid transport by a mechanism involving protein synthesis at a stage later than transcription whereas high doses of the hormone inhibit fluid transport by a process which does not require protein synthesis.

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K. A. MUNDAY
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B. J. PARSONS
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JUDITH A. POAT
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D. J. SMITH
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The presence of calcium in the fluid in which intestinal or kidney tissue is incubated is required for the tissue to respond to angiotensin. Everted sacs of rat colonic mucosa exhibited an increased rate of fluid transport in the presence of angiotensin; this response was lost when the serosal fluid, but not the mucosal fluid, was calcium-free. Angiotensin-stimulated transport was maintained when calcium was replaced with strontium or barium, but was lost when calcium was exchanged for magnesium. Similarly, calcium ions were required in the incubation fluid of rat kidney cortex slices to demonstrate angiotensin-enhanced sodium transport. These observations are discussed in relation to the possible roles of divalent cations in the mechanism of action of angiotensin.

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K. A. MUNDAY
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B. J. PARSONS
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JUDITH A. POAT
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GHISLAINE A. D'AURIAC
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P. MEYER
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Department of Physiology and Biochemistry, University of Southampton, Southampton, S09 3TU and *Department of Physiology and Pharmacology, INSERM U7, Hopital Necker, 75015 Paris, France

(Revised manuscript received 21 January 1976)

Angiotensin has a number of actions which include stimulation of sodium transport by rat colon and kidney (Parsons & Munday, 1972). Attempts to implicate cyclic AMP as a mediator of angiotensin responses have proven inconclusive. Kaplan (1965), Davies, Munday & Parsons (1972) and Munday, Parsons & Poat (1972) were unable to mimic angiotensin responses with cyclic AMP derivatives or theophylline, whereas Coviello (1973) and Hornych, Meyer & Milliez (1973) obtained angiotensin-like effects following the application of cyclic AMP. The possible involvement of cyclic AMP in the responses of intestine and kidney has been re-assessed using direct measurements of adenyl cyclase activities and tissue cyclic AMP concentrations in two independent laboratories.

Fluid and sodium transport was measured in stripped sacs of

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P. G. DOREY
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K. A. MUNDAY
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B. J. PARSONS
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JUDITH A. POAT
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MARY E. UPSHER
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A study has been made of the effects of chemical sympathectomy and ganglion blockade on the responses of rat jejunum in vivo to intravenous doses of angiotensin and noradrenaline capable of stimulating fluid transport. Pretreatment with 6-hydroxydopamine (chemical sympathectomy) or pentolinium tartrate (ganglion blockade) abolished the stimulatory actions of angiotensin II but left the responses to noradrenaline unimpaired. Dopamine, like noradrenaline, stimulated fluid transport but this response required very high dopamine infusion rates, was refractory to the dopamine antagonist sulpiride and was inhibited by the α-blocker phentolamine.

The possible interaction between angiotensin and the intestinal sympathetics is discussed with reference to control of extracellular fluid volume.

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J. L. H. O'RIORDAN
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J. S. WOODHEAD
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G. N. HENDY
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J. A. PARSONS
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C. J. ROBINSON
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H. T. KEUTMANN
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B. F. DAWSON
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J. T. POTTS Jr
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SUMMARY

The presence of a single methionine in porcine parathyroid hormone, at position 8, permitted assessment of the role of this residue separate from the second methionine residue found at position 18 of bovine and human parathyroid hormones. Oxidation of the solitary methionine of porcine parathyroid hormone to the sulphoxide destroyed biological activity, but this was restored by subsequent reduction with cysteine. Oxidation of the hormone did not, however, affect its immunological activity; therefore, oxidation of the hormone may bring about dissociation of biological and immunological activity.

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N. J. MacLusky
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L. C. Krey
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B. Parsons
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G. R. Merriam
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D. L. Loriaux
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D. G. Pfeiffer
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F. Naftolin
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ABSTRACT

The role of catechol oestrogen formation in the mechanism by which circulating oestrogens facilitate gonadotrophin release and female sexual behaviour was explored in adult female rats. The effects of oestradiol-17β were compared with those of a group of oestrogens with either a reduced affinity for oestrogen receptors (oestradiol-17α) or a reduced ability to act as substrates for catechol oestrogen formation (2-fluoro-oestradiol, 4-fluoro-oestradiol and moxestrol (11β-methoxy-17α-ethynyloestradiol)). Rats were ovariectomized on the evening of dioestrus day 1 of the 4-day oestrous cycle and implanted s.c. 12 h later with infusion pumps containing either one of the test oestrogens or vehicle alone. Infusion rates for oestradiol-17β, moxestrol, 2-fluoro-oestradiol and 4-fluoro-oestradiol were adjusted to give concentrations of nuclear oestrogen receptors in the brain and pituitary gland within the range of those found in intact female rats during pro-oestrus. Oestradiol-17α was infused at the same and at a tenfold higher rate than that of oestradiol-17β; neither of these treatments with oestradiol-17α significantly increased brain or pituitary gland nuclear oestrogen receptor levels. On the day after the pump was implanted, samples of tail vein blood were withdrawn at 12.00, 14.00, 16.00 and 18.00 h for LH assay. All animals were then injected s.c. with 1 mg progesterone in propylene glycol, and tested for feminine sexual behaviour 5 h later. Oestradiol-17β, moxestrol, 2-fluoro-oestradiol and 4-fluoro-oestradiol all elicited pronounced LH surges and facilitated progesterone-triggered proceptive and lordosis behaviours. In contrast, oestradiol-17α was without effect on LH secretion and sexual behaviours. These results are consistent with the hypothesis that catechol oestrogen biosynthesis is not an obligatory step in the mechanism by which circulating oestrogens induce LH release and feminine sexual behaviour in the rat.

J. Endocr. (1986) 110, 499–505

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