Effects of β-agonist, L-644,969, on adipose depots in growing female rats

Abstract

Growing female Sprague Dawley rats (n = 33) were used to determine the effects of β-agonist, L-644,969, on adipose depots, mammary growth and plasma ST and IGF-I levels. Fat-cell diameter in SF and PF, and mammary DNA content were studied. Rats were allocated to three groups to receive 0,4 or 8 mg kg−1 L-644,969 in powdered diet for 35 d. Compared with control, total mammary gland weight, as a proportion of final body weight, was reduced 14.6 (P < 0.05) and 35.6% (P < 0.01), PF was reduced 30 and 49.6% (both P < 0.01) by 4 and 8 mg kg−1, respectively. The SF was reduced 22.3% (P < 0.05) by β-agonist at 8 mg kg−1 only. In all fat depots, the reductions increased with increasing dose of β-agonist. Carcass fat percentage was reduced by 28.5 and 41.7% (both P < 0.01) in rats fed β-agonist at 4 and 8 ppm, respectively. 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 concentration but to lower IGF-I concentration as β-agonist levels in diet increased (P > 0.1). The results indicate that β-agonist is effective in reducing body fat deposition and fat-cell size and stimulating mammary gland growth, which may play a role in the control of mammogenesis in growing rats. Key words: Rats, β-agonist, mammary gland, adipose tissue