Body fat accumulation in the guinea pig.

Abstract

Seventy-two guinea pig carcasses divided into three series: a) adult, b) growth (4 days to 8 months) and c) exercise (adults on an exercise regimen) were separated into eleven gross body components by dissection. Each component was freeze dried and extracted with ethyl and petroleum ether. Distribution of fat and the fat content of the gross components were studied statistically. Accretion of fat in all three series is accomplished primarily by saturating existing adipose tissue, and secondarily by an increase in either number or size of lipocytes. Females have an appreciably larger fat storage capacity than males without resorting to either lipocyte proliferation or hypertrophy. Except in immature individuals the fraction of total body fat in subcutaneous and in internal depots is constant at all levels of body fatness. Males have 6–7% less of their total fat in the subcutaneous depot and proportionately more in the internal depots than do females. Fat depots account for about 95% of total body fat, most of the remainder being distributed among gut, bone, liver, kidneys and heart. In all three series with increasing body fatness these organs acquire additional fat, but in each case the rate of fat accretion is less than that of the body as a whole. Fat distribution to the organs appears similar in the two sexes. Body fatness in the adult series was shown to be related to specific gravity of the eviscerated carcass by the following equation: (See PDF)