Effect of the Growth Hormone-Secreting Tumor StW5 on Pituitary and Adrenal Gland Function in Rats

Abstract

A growth hormone-secreting tumor (StW5) was implanted into male rats and resulted in a tripling of adrenal weight concomitant with a 30% decrement in pituitary weight. Plasma concentrations of corticosterone in tumor-bearing (TB) rats were significantly elevated at rest or after ACTH injections or the stress of ether anesthesia. The rise in plasma concentrations of corticosterone was due mainly to the large increment in adrenal size although a significant increase in adrenal responsiveness to ACTH was demonstrated in vitro. In addition, plasma corticosterone concentrations were higher in TB rats despite both a doubling of the blood volume and a 50% increase in liver capacity to metabolize corticosterone. Pituitary ACTH content was significantly lower in TB rats, but these pituitary glands could still release near-normal quantities of ACTH as shown both by in vitro incubations and adrenal corticosterone output following ether stress.

Changes in serum concentrations of ACTH, corticosterone and in growth following morning or evening injection of female rats with porcine growth hormone

“…This finding contrasts with the reported increased adrenal responsiveness to ACTH in GH-treated, hypophysectomized rats (Colby, Caffrey & Kitay, 1973;Kramer, Greiner & Colby, 1977) and in intact animals implanted with GH-secreting tumours (Coyne, Alpert, Harter & Nunez, 1981). However, in an earlier study using normal animals, Bates, Milkovic & Garrison (1964) observed a significant attentuation of the corti¬ costeroid response to ACTH injection in rats treated concomitantly with bovine GH and prolactin.…”

“…A similar trend was observed in the present study when corticosterone values determined for the morning and afternoon samples were pooled. In addition, rats implanted with GHsecreting tumours are reported to have higher basal concentrations of corticosterone (Coyne et al 1981). …”

Increased plasma corticosterone levels in bovine growth hormone (bGH) transgenic mice: Effects of ACTH, GH and IGF-I onin vitro adrenal corticosterone production

“…increase plasma corticosterone without changes in ACTH secretion (Coyne et al, 1981), we originally hypothesized that, in these transgenic mice, GH was acting at the adrenal level to stimulate corticosterone production as was proposed previously for other models (Colby et al, 1973;Kramer et al, 1977): Even though adrenals of transgenic as compared with normal mice apparently produce greater amounts of corticosterone in vivo, once removed from the high GH environment they behave very similarly to adrenals removed from non-transgenic animals. Moreover, the corticosterone response of normal and transgenic adrenals to different doses of ACTH did not differ.…”

“…Coyne et al (1981) transplanted pituitary tumours which produced GH only, and found a 300% increase in adrenal weight and 30% reduction in pituitary weight. Blood corticosterone was elevated despite increases in plasma volume, rate of steroid metabolism, and liver size.…”