Suppression of the Luteinizing Hormone Releasing Effect of Luteinizing Hormone Releasing Hormone by Arginine-Vasotocin

Abstract

The concentrations of 17-oxosteroids in the spermatic venous blood of anaesthetized dogs were used as an index of LH release to assess the effects of arginine-vasotocin on the response of the canine pituitary gland to exogenous luteinizing hormone releasing hormone (LH-RH). When injected into the carotid artery, arginine-vasotocin (1.0 microgram/kg body wt) caused no significant alterations in the testicular output of 17-oxosteroids. The administration of LH-RH (5 microgram/kg body wt, a standard dose) into the carotid artery produced typical stimulation of testicular 17-oxosteroid secretion. Administration of arginine-vasotocin (0.01, 0.1 or 1.0 microgram/kg body wt) into the carotid artery 3 h before the administration of a standard dose of LH-RH inhibited the testicular secretion of 17-oxosteroids normally induced by LH-RH. However, pretreatment with arginine-vasotocin (1.0 microgram/kg body wt) did not affect the testicular response to i.v. administration of human chorionic gonadotrophin (5 i.u./kg body wt). These results indicate that in the dog, arginine-vasotocin inhibits the LH-RH-induced release of LH by acting acting directly on the anterior pituitary gland.

Suppression of the Luteinizing Hormone Releasing Effect of Luteinizing Hormone Releasing Hormone by Arginine-Vasotocin in Immature Male Dogs

“…Since the testicular response to the administration of HCG was unaffected by treatment with argininevasotocin, it is likely that the suppression of testicular steroid secretion observed was due to an effect on the anterior pituitary gland and not to a direct action of arginine-vasotocin on the testes. Although it is known that arginine-vasotocin may act within the .brain to inhibit the secretion of LH (Pavel, Dorcescu, Petrescu-Holban & Ghinea, 1973;Osland, Cheesman & Forsham, 1977;Vaughan, Blask, Johnson & Reiter, 1979), the present data suggest that arginine-vasotocin is able to antagonize or to modify the action of LH-RH on the anterior pituitary gland in immature dogs, as in mature ones (Yamashita et al 1979).…”

“…In our studies, the potency of arginine-vasotocin in suppressing the LH releasing activity of LH-RH appears to be greater in immature animals than in mature animals (Yamashita et al 1979) and was also approximately ten thousand times more potent than melatonin ). These findings, therefore, raise the possibility that arginine-vasotocin might also be involved in pubertal development.…”

“…Since this cannulation technique permitted the collection of the total venous effluent from the left testis, the rate of flow (ml/kg body wt per min) of spermatic venous blood could be estimated. Arginine-vasotocin (Protein Research Foundation, Osaka, Japan; 0-1 or 10 ng/kg body wt) was injected into the left carotid artery, 10 ng/kg body wt having been reported to inhibit the action of LH-RH in mature male dogs (Yamashita et al 1979). Control animals received 0-9% saline only.…”

“…A previous study (Yamashita, Mieno & Yamashita, 1979) showed that the pineal peptide arginine-vasotocin (Milcu, Pavel & Neacsu, 1963;Pavel & Petrescu, 1966;Cheesman & Fariss, 1970) acted directly on the anterior pituitary gland in mature male dogs to inhibit the effect of luteinizing hormone releasing hormone (LH-RH) in the release of luteinizing hormone (LH). In this study, the effect of the peptide was examined in immature male dogs using the secretion of 17-oxosteroids by the testes as an index of LH secretion (Yamashita, 1966;Yamashita, Mieno, Shimizu & Yamashita, 1978).…”

Effects of luteinizing hormone-releasing hormone and arginine-vasotocin on the sperm-release response of Günther's Toadlet, Pseudophryne guentheri

“…The inhibition of gonadal activity by AVT has also been reported in other vertebrate taxa, including reptiles and mammals [34-37]. Additionally, Yamashita et al [38] discovered that the mechanism underlying the antigonadal action of AVT in the dog involved the AVT-induced suppression of LH release by the anterior pituitary. Their study showed that AVT administered prior to LHRH inhibited testicular activity, but that AVT did not affect testicular activity when administered prior to human chorionic gonadotropin (hCG).…”