histrelin and Body-Weight

The effects of synthetic luteinizing hormone-releasing hormone (LHRH) (0.01 and 0.1 microgram) agonist on pituitary and ovary were studied in the juvenile frog Rana cyanophlyctis with respect to their body weights. Injections (ip) were given 6 days a week for 30 days and frogs were sacrificed on the 31st day. The pituitary sections were stained with AB-PAS-OG technique. The staining intensity, cytoplasmic granulations, and length of hypophysial gonadotrophs (B2 cells) were increased (P less than 0.05) due to LHRH treatment. In controls, the B2 cells were small and faintly stained. Treatment with LHRH (0.01 or 0.1 microgram) once a day or twice a day (0.01 microgram) to frogs weighing less than 6 g body weight had no effect on gonadosomatic index (GSI) or size frequency distribution of oocytes even though gonadotrophs were hypertrophied and hyperactive. Whereas administration of LHRH (0.01 or 0.1 microgram) once a day to frogs weighing around 8 g caused a significant (p less than 0.05) increase in ovary weight, GSI, and diameter of the largest oocytes. Further, oocytes were recruited to second growth phase (i.e., incorporation of yolk in oocytes) due to LHRH treatment. The above findings suggest that synthetic LHRH agonist has the stimulatory effect on oocyte growth and recruitment of vitellogenic oocytes in juvenile frogs weighing around 8 g. The LHRH induces precocious maturity by incorporating yolk in oocytes. The pituitary responsiveness to LHRH agonist is also evident in juvenile frogs. The ovarian receptivity/responsiveness to endogenous gonadotrophins seems to progressively increase with the increase in the body weight of the juvenile frogs.

Topics: Animals; Body Weight; Female; Gonadotropin-Releasing Hormone; Ovary; Pituitary Gland; Ranidae

The antigonadal activity of potent gonadotropin-releasing hormone (GnRH) analogs may be associated with undesirable secondary effects on other aspects of the endocrine system. In preliminary studies, rats treated with GnRH agonists were noted to have altered adrenal weights. To determine whether this was associated with alterations in the pituitary-adrenal axis we have studied male and female rats treated with the GnRH agonist [(imBzl)-D-His6, Pro9-NEt]-GnRH (GnRH-A). Animals receiving daily doses of this peptide showed normal adrenal corticosteroid responsivity to both ether and immobilization stress. Brain, pituitary, and plasma concentrations of immunoreactive (IR) beta-endorphin and ACTH were unaffected in treated animals after four weeks of daily injections, although after one week plasma levels of the two hormones were transiently elevated in female rats. Adrenal, thyroid, and pituitary lobe weights were unchanged with treatment, except for an increase in anterior pituitary weight in males receiving the lowest dose of GnRH-A. In conclusion, long-term treatment with GnRH-A, while significantly affecting gonadal and secondary sexual tissue, had little impact on the hypothalamo-pituitary-adrenal system or on stress responsivity in rats.

Topics: Adrenal Glands; Adrenocorticotropic Hormone; Animals; beta-Endorphin; Body Weight; Castration; Corticosterone; Endorphins; Ether; Female; Gonadotropin-Releasing Hormone; Hypothalamus; Immobilization; Male; Pituitary Gland; Rats; Rats, Inbred Strains; Stress, Physiological