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D. T. DAVIES and J. COLLINS

SUMMARY

After the i.m. injection of 10 μg synthetic LH releasing hormone (LH-RH) into Japanese quail the levels of LH and FSH in plasma rose significantly within 2 min. The increased level of LH declined rapidly but that of FSH was maintained for the duration of the experiment. To determine whether the anterior pituitary gland is primed by LH-RH a double injection schedule was adopted. It would appear that, while endogenous LH-RH may prime the avian pituitary gland slightly, synthetic LH-RH is ineffective.

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T. A. Parkening, T. J. Collins and E. R. Smith

Plasma levels of LH were measured in young sexually mature (2- to 5-month-old) and aged (13- to 20-month-old) female C57BL/6 mice, Syrian hamsters and Wistar rats using a radioimmunoassay (RIA) and a radioreceptor assay (RRA). There were no statistically significant differences when comparing data from the two assays when examining young oestrous and dioestrous mice. Aged oestrous and dioestrous mice exhibited significantly higher levels of LH as measured by RIA than by RRA. Levels of LH analysed by RIA were also higher in aged mice compared with those in younger mice. Comparing LH concentrations with the two types of assays in younger dioestrous and aged anoestrous hamsters produced similar results. In contrast, aged pseudopregnant rats exhibited significantly lower levels of plasma LH than younger dioestrous females and there were no differences in RIA and RRA values. There were also no differences when comparing data from the two assays in younger rats. The mean (± s.e.m.) RRA: RIA ratios of 0·96 ± 0·05 (oestrous) and 0·96 ± 0·04 (dioestrous) for younger mice and 0·92 ± 0·08 for younger hamsters were significantly higher than the ratios of 0·66 ± 0·72± 0·05 and 0·71 ± 0·05 respectively of their aged counterparts. The mean RRA: RIA ratios in the two age groups of rats were almost identical (0·79 ± 0·05 and 0·80 ± 0·10). These studies suggested that a portion of the higher LH levels detectable by RIA in some aged female rodents results from qualitative changes in the LH molecule.

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A T Collins, E J Robinson and D E Neal

Abstract

The current study was undertaken, using cultures of prostatic epithelial and stromal cells, to determine the functional interactions between androgens, basic fibroblast growth factor (FGF2) and transforming growth factor-β1 (TGFβ1) and their importance in maintaining stromal homeostasis. Treatment of stromal cells with TGFβ1 significantly increased intracellular FGF2 and FGF2 sequestered to the extracellular matrix. FGF2 was also detected in stromal conditioned medium (SCM), but at levels 70-fold less than found in cell lysates. TGFβ1 (0·1 ng/ml) treatment caused an initial increase of 86% in secreted FGF2 levels, but high concentrations of TGFβ1 (5 ng/ml) decreased FGF2 levels by 38%, relative to the untreated control. Further studies showed that epithelial conditioned medium (ECM), androgen-treated, stromal conditioned medium (ASCM), but not SCM were mitogenic for stromal cells. Both ECM and ASCM caused a threefold increase in DNA synthesis. FGF2 may be the mediator of these interactions, since the mitogenic effect of both ECM and ASCM was significantly reduced by the addition of anti-FGF2 neutralising antibody. We hypothesise that the lack of response of stromal cells to SCM is due to TGFβ1 blocking the mitogenic effect of FGF2. Thus down-regulation of TGFβ1 synthesis, by androgens, results in stromal proliferation by ASCM.

Journal of Endocrinology (1996) 151, 315–322

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A. Bartke, W. W. Morgan, R. N. Clayton, T. K. Banerji, A. M. Brodie, T. A. Parkening and T. J. Collins

ABSTRACT

In several species, including man and the rat, hyperprolactinaemia is associated with suppression of gonadotrophin release and male sexual behaviour. However, in the hyperprolactinaemic male mouse, plasma LH and FSH levels and copulatory behaviour are increased rather than suppressed. In an attempt to identify mechanism(s) which may be responsible for these effects of hyperprolactinaemia in the mouse, we have examined the effects of two ectopic pituitary isografts on several indices of hypothalamic and pituitary function in adult DBA/2J males. Animals with pituitary grafts had markedly increased plasma concentrations of prolactin, LH and FSH and enlarged seminal vesicles, whereas testicular and pituitary weights were not affected. Content of LHRH receptors and activity of aromatase in the pituitary, as well as dopamine-β-hydroxylase activity in the hypothalamus were nearly identical in pituitary-grafted and sham-operated males. Biosynthesis of dopamine and turnover of noradrenaline in the median eminence were significantly increased in grafted males. We suggest that the increase in the activity of hypothalamic noradrenergic neurones may mediate stimulatory action of hyperprolactinaemia on LH and FSH release in the mouse. Comparison of these results with those obtained previously in the rat suggests that species differences in the effects of prolactin on gonadotrophin release may be related to its divergent effects on noradrenaline turnover.

J. Endocr. (1987) 112, 215–220