The Long Term Effect of Estrogen Administration on the Metabolism of Male Rat Bone

Abstract

Hundred and fifty-gram male rats were divided into four groups with the first containing intact controls, the second intact animals treated with 400 μg per 100 g body wt of 17-β-estradiol twice a week. The animals in the third group were castrated and those in the fourth were castrated and treated with the same dosage of estrogen. Animals were sacrificed at varying periods of time from one to 12 months. Estrogen administration caused a sustained decrease in body weight in the intact animal but did not change the body weight in castrated animals. Estrogen had no effect on either serum calcium or serum phosphorus. Estrogen administration to the intact animal caused a small but significant increase in ash content of bone. Castration caused a small decrease in this value which was still present at 12 months and estrogen administration returned the value to normal. Estrogen administration caused a decrease in total hydroxyproline content of bones of intact animals. Castration did not alter this value but estrogen administration to the castrated animal decreased the bone hydroxyproline content. Hydroxyproline incorporation rates were decreased in bones of both the intact and castrated animals. Castration did not alter the total hexosamine content of bones but estrogen administration to both the intact and castrated animals caused an increase in bone hexosamine content. Estrogen administration caused a decrease in the synthesis rate of proteoglycans in bones of both the intact and castrated animals. Estrogen administration caused a decrease in the uptake of radioactive calcium into bones of both the intact and castrated animals. There was no significant effect of estrogen on collagenolytic activity in male rat bone. It is concluded that estrogen administration to the male rat, causes changes which are different from those found in the female. There appeared to be no change in serum calcium or phosphorus values. A decreased synthesis of bone matrix and decreased uptake of radioactive calcium brought about no measurable change in the resorption of bone matrix.