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Search for other papers by C. W. LLOYD in
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SUMMARY
The effects of heterotopic pituitary homografts on the weight of the accessory reproductive structures, submandibular glands and kidneys were studied in castrated, castrated—adrenalectomized and castrated—hypophysectomized male rats and mice. In rats no consistent effects were seen; in mice the weights of the seminal vesicles, submandibular glands and kidneys were increased. When castrated mice were treated with prolactin or growth hormone (GH), singly or combined, the seminal vesicles responded to all three treatments at certain dose levels, while the submandibular glands were affected by GH only. The effects of pituitary isografts were compared in castrated and in intact hereditary dwarf mice. The weight of the submandibular glands was increased in both groups but that of the seminal vesicles only in intact dwarfs. It was concluded that in male mice prolactin exerts a small testis-independent influence on the reproductive system, and may also increase the production of androgen by the testis. Pituitary grafts had no effect on the restoration of mating behaviour in either castrated or castrated—hypophysectomized male mice treated with testosterone propionate.
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This work was undertaken to study the influence of purified prolactin on spermatogenesis in hypophysectomized rats with or without testosterone propionate maintenance therapy and in prolactin-deficient hereditary dwarf mice. In addition some dwarf mice were given heterotopic isografts of non-dwarf mice pituitaries. In rats, 25 i.u. ovine prolactin given daily for 33 days had no effect on the maintenance of spermatogenesis. In untreated dwarf mice spermatogenesis progressed to completion but had a low yield due to cell loss, especially during premeiotic divisions. Both 10 i.u. prolactin daily for 28 days and pituitary grafts resulted in marked stimulation of spermatogenesis. The number of preleptotene and pachytene spermatocytes and step 7 spermatids was significantly increased in both inbred and F1 dwarf mice regardless of age. Since seminal vesicles were also considerably heavier in treated dwarfs, it was concluded that the observed stimulation of spermatogenesis was most likely due to elevated testicular androgen production indicating that, in the male mouse, prolactin may be involved in pituitary regulation of Leydig cell function.
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Search for other papers by C. W. LLOYD in
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Hypophysectomized adult male rats were treated twice daily for 3½ days with 0·9% NaCl solution, 200 μg ovine prolactin, 5 μg ovine luteinizing hormone (LH), or 200 μg prolactin +5 μg LH, starting 18 days after the operation. Minced testes from these animals were incubated in Krebs—Ringer bicarbonate buffer containing [1-14C]acetate for 3 h at 37 °C. The conversion of acetate into testosterone was calculated. It was not changed by prolactin treatment, was increased by LH (P < 0·01), and further increased by prolactin + LH (P < 0·01) to approximately the level observed in intact adult controls. The amount of testosterone in some of the incubates was measured by gas liquid chromatography. It was not changed in prolactin-treated animals and was increased in LH-treated animals (P < 0·02 compared with hypophysectomized controls). Treatment with prolactin+LH resulted in an increase in testosterone above that after treatment with LH alone (P < 0·01) and to a value similar to that in intact adult males. The incorporation of acetate into esterified cholesterol was decreased (P < 0·05) in groups treated with LH or prolactin + LH in which testosterone synthesis was increased. The incorporation of acetate into free cholesterol was not changed by any of the treatments. These results demonstrate synergistic action of prolactin and LH on the synthesis of testosterone in vitro confirming our earlier suggestions.
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Search for other papers by C. W. LLOYD in
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Search for other papers by A. BARTKE in
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SUMMARY
Testosterone and androstenedione levels in the plasma of hypophysectomized rats were measured by a protein-binding method (sensitivity 150 pg testosterone; precision, 10%).
Testosterone levels in the plasma of saline-treated hypophysectomized rats were undetectable (<0·3 ng/ml). Administration of 200 μg prolactin twice daily s.c. for a period of 3½ days caused a slight rise in testosterone in four rats (0·61 ± 0·35 ng/ml) while 5 μg luteinizing hormone (LH) administered in the same regimen increased testosterone levels to 1·42 ± 0·35 ng/ml (P < 0·05). Administration of prolactin ± LH (same doses) increased testosterone levels to 5·07 ± 0·51 ng/ml which is significantly higher than when LH was given alone and exceeds testosterone levels in intact adult males (4·12 ± 0·60 ng/ml).
Androstenedione levels in the plasma of saline-treated hypophysectomized rats were, in contrast to testosterone levels, very high and averaged 3·37 ± 0·60 ng/ml. This level is higher than that in saline-treated intact controls (1·89 ± 0·36 ng/ml). Treatment with prolactin, LH or prolactin + LH induced insignificant changes in androstenedione levels which were 1·80 ± 0·33, 2·02 ± 0·28 and 4·22 ± 0·75 ng/ml, respectively.
The ratio testosterone: androstenedione was calculated to be 0·37 ± 0·08 in the prolactin-treated group, 0·76 ± 0·20 in the LH-treated group and 1·47 ± 0·64 in the prolactin + LH-treated group compared with 2·36 ± 0·28 in intact control males.
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Coffey, Ichinose, Shimazaki & Williams (1968) and Ritter (1966) have demonstrated that 2 weeks after castration the concentration of ATP in the rat ventral prostate remains unchanged from normal levels but that 1 h after testosterone treatment dramatic reductions in ATP concentrations are observed. The cellular site of testosterone action upon ATP metabolism is unknown. In a complex tissue such as the prostate it is difficult, if not impossible, to examine separately the biochemistry of the epithelium and muscle; this can be effectively surmounted using the guinea-pig seminal vesicle. From this, a relatively pure preparation of epithelium can be obtained, and the biochemical sensitivity of these two cell lines may be compared. It is the purpose of this work to examine the effects of castration and testosterone replacement upon the levels of ATP in the epithelium and muscle of the guinea-pig seminal vesicle as well as in the prostate.
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Search for other papers by C. W. LLOYD in
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SUMMARY
Vasopressin content and the staining of neurosecretory material with chrome-alum-haematoxylin-phloxin were observed in the neurohypophysis of rats following injection of formalin. The amount of neurosecretory material was reduced during the period up to 90 min. after formalin injection while no change in the vasopressin content was observed. These observations support the concept that the neurosecretory material is distinct from vasopressin and may be acting as a carrier or precursor for the hormones of the neurohypophysis.