Changes in growth hormone secretion in spontaneously hypertensive rats.
Secretion of the growth hormone (GH) in spontaneously hypertensive (SH) male rats has been determined and compared with that of normotensive Wistar-Kyoto (WKY) controls. In a first set of experiments, plasma GH concentration and pituitary GH content were measured in SH rats 30, 60 and 90 days old. 30-day rats showed reduced GH plasma and pituitary levels, whereas in 60- and 90-day-old rat no differences in GH plasma concentration and increased GH pituitary content were observed. In a second set of experiments, 90-day-old SH male rats anesthetized with sodium pentobarbital and intravenously injected with growth hormone-releasing factor (GRF) showed an amplitude and duration of response to injected hormone higher than WKY controls. In a third set of experiments, hemipituitaries of 90-day-old SH males were incubated for 2 h in Krebs-Ringer-bicarbonate either in the presence or in the absence of GRF. In the absence of GRF stimulation, the in vitro release of GH was higher than in WKY controls, whereas in the presence of GRF the sensitivity and the maximum response to GRF was reduced in comparison with normotensive male rats. These results indicate that SH rats have decreased pituitary content and plasma GH concentration before puberty. Besides, they showed increased pituitary GH content in adulthood and opposite changes in the in vivo and in vitro response to GRF.
Aguilar
E
E
Department of Physiology, Faculty of Medicine, Córdoba University, Spain.
Rodríguez
M L
ML
Bellido
C
C
de la Fuente
M
M
Pinilla
L
L
D000818:Animals; D013006:Growth Hormone / Q000097:blood / Q000378:metabolism*; D013007:Growth Hormone-Releasing Hormone / Q000494:pharmacology; D006973:Hypertension / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D009929:Organ Size; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D013739:Testosterone / Q000097:blood
D013739:Testosterone; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone