EFFECTS OF BETA-AGONIST, L-644,969, ON ADIPOSE DEPOTS IN GROWING FEMALE RATS

Growing female Sprague Dawley rats (n = 33) were used to determine the effects of beta-agonist, L-644,969, on adipose depots, mammary growth and plasma ST and IGF-I levels. Fat-cell diameter in SF and PF, and m ammary DNA content were studied. Rats were allocated to three groups t o receive 0,4 or 8 mg kg(-1) L-644,969 in powdered diet for 35 d. Comp ared with control, total mammary gland weight, as a proportion of fina l body weight, was reduced 14.6 (P < 0.05) and 35.6% (P < 0.01), PF wa s reduced 30 and 49.6% (both P < 0.01) by 4 and 8 mg kg(-1),respective ly. The SF was reduced 22.3% (P < 0.05) by beta-agonist at 8 mg kg(-1) only. In all fat depots, the reductions increased with increasing dos e of beta-agonist. Carcass fat percentage was reduced by 28.5 and 41.7 % (both P < 0.01) in rats fed beta-agonist at 4 and 8 ppm, respectivel y. Fat-cell diameter in both SF and PF was reduced (P < 0.05) (except at 4 ppm level in SF), and mammary DNA content was increased (P < 0.01 ) in both treatment groups. There was a trend to increased ST concentr ation but to lower IGF-I concentration as beta-agonist levels in diet increased (P > 0.1). The results indicate that beta-agonist is effecti ve in reducing body fat deposition and fat-cell size and stimulating m ammary gland growth, which may play a role in the control of mammogene sis in growing rats.