In vivo and in vitro responses to gonadotropin releasing hormone in the turtle, XXXX , in relation to sex and reproductive stage.

@entity29551 @entity251 @entity1176
In vivo and in vitro responsiveness to gonadotropin releasing hormone ( @entity1176 ) was studied in the turtle, @entity29551 , after manipulation of reproductive condition by temperature: Warm temperatures (28 degrees) induced testicular growth and ovarian regression compared to cold (17 degrees) treatment. Only males (and primarily from cold treatment) responded to @entity1176 injection (40 micrograms/100 g body wt intracardiac); correlated increases occurred in plasma LH and @entity251 . Effects of @entity1176 (10 and 100 ng/ml) on LH and FSH secretion by hemipituitaries were studied in a superfusion system; tissues responded to between 0.1 and 1 ng/ml @entity1176 . Sex differences were evident in both acute and chronic effects of @entity1176 . Although both groups of females had significantly (sixfold) higher pituitary LH content, basal secretion rates of gonadotropins were similar, and LH and FSH secretion in males was more responsive to @entity1176 . Gonadotropin secretion rates by male glands showed high initial increments (approx four- to sevenfold) followed by an attenuation (especially LH) during 5 hr of @entity1176 superfusion. In contrast, tissues from warm-treated females showed a smaller initial response (approx twofold) followed by a progressive increase in output over time, and glands from cold-treated females did not respond to @entity1176 . Total LH secretion by superfused male hemiglands represented almost half the total LH recovered (secreted + stored); whereas, females secreted only 5% ("cold-treated") or 10% ("warm-treated") of total LH. Thus, the capacity of the pituitary to respond to @entity1176 is influenced by both sex and reproductive condition in the turtle. Secretion of both FSH and LH were similarly stimulated by @entity1176 , but thyrotropin (TSH) secretion was independent of @entity1176 .
