EFFECTS OF ANDROGENS, OESTROGENS AND DEOXYCORTICOSTERONE ACETATE ON PLASMA CONCENTRATIONS OF LUTEINIZING HORMONE IN LAYING HENS

Abstract

SUMMARY: Testosterone, androstenedione, oestrone, oestradiol-17β or deoxycorticosterone acetate (DOCA) were injected intramuscularly at several dose-levels and at various stages of the ovulatory cycle, and subsequent changes in plasma LH concentration were measured by radioimmunoassay. In 19 out of 24 hens, injection of 0·1, 0·5 or 1·0 mg DOCA/kg resulted in a mean maximal increase in plasma LH concentration of between 0·47 and 2·10 ng/ml. The magnitude of this response was not related to either the dose or the stage of the cycle at which the DOCA was injected. In the remaining five hens DOCA failed to stimulate LH secretion. Injection of either androstenedione, oestrone or oestradiol did not result in any increase in LH level in the circulation. In contrast, injection of 0·5, 1·0 or 2·0 mg testosterone/kg between 22 and 26 h after the terminal ovulation of a sequence resulted in mean maximal incremental changes in plasma LH level of 1·98 ± 0·17, 2·17 ± 0·21 and 2·41 ± 0·31 (s.e.m.) ng/ml from pre-injection values of 1·38 ± 0·16, 1·58 ± 0·30 and 1·43 ± 0·39 ng/ml (n = 7, 6 and 5, respectively). The interval between the injection and the resulting rise in LH level was inversely proportional to the dose. The same doses of testosterone injected between 0 and 8 h after ovulation failed to stimulate LH secretion. There was also no significant increase in LH levels after injection of 0·5 and 1·0 mg testosterone/kg between 8 and 9 h after ovulation. However, injection of 2 mg testosterone/kg at this time resulted in a small but significant (P < 0·05) increase in LH levels. Since the largest ovarian follicle is more mature at 22–26 h after ovulation than at 0–9 h after ovulation, the ability of testosterone to cause the release of LH therefore appears to depend upon the degree of maturation of the ovarian follicle next due to ovulate.