Growth hormone-secretory patterns in androgen-resistant (testicular feminized) rats.

To investigate the role of androgen receptors in the expression of the male GH-secretory pattern in adult rats, the GH-secretory patterns in androgen-resistant (testicular feminized) rats were compared with their normal male and female littermates. All animals were prepared with intraatrial Silastic catheters and bled every 15 min for 8 h (0800-1600 h). Normal male littermates displayed a characteristic low frequency, high amplitude pattern of GH secretion with bursts of GH occurring every 2.5-3 h and separated by prolonged trough periods where GH values remained low or undetectable (less than 5 ng/ml) for 45-90 min. Normal female littermates showed a characteristic high frequency, low amplitude pattern of GH secretion with pulses of GH occurring every hour. Compared to normal male littermates, females had lower individual GH peak amplitudes and shortened GH-trough periods which contain higher GH levels. GH-secretory profiles displayed by testicular-feminized animals qualitatively and quantitatively resembled those of the normal female littermates. These data suggest that androgen receptors are necessary for the expression of masculine GH-secretory patterns.