High Dosage of Testosterone Propionate Increases Litter Production of the Genetically Obese Male Zucker Rat

Abstract
A high dose of testosterone proprionate [TP] increases dramatically the litter production of young genetically obese male Zucker rats. Testosterone 20 mg injected s.c. once every 3 days over a 90 day period resulted in a nearly 4-fold increase in the number of litters sired compared to sham-injected controls. The efficacy of the treatment attenuates with time. TP was ineffective in inducing litter production in older, more obese, males. Young obese males injected with TP exhibited a significantly reduced rate of weight gain compared to sham-injected controls. The findings are consistent with the hypothesis that the reproductive inadequacy of the genetically obese male rat may be due to a deficiency of circulating testosterone. The treatment of obese males with TP greatly increases the efficiency with which the obese (fafa) genotype may be produced and also avoids time-consuming testcrossing for identification of heterozygous (Fafa) individuals.

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