Effects of Parathyroid Extract, Dihydrotachysterol (Hytakerol) and Calciferol on Milk Secretion in Rats1

Abstract

A 8tudy was made of the effects of parathyroid extract (PTE), dihydrotachysterol (Hytakerol) and calciferol on milk secretion in rats. Thirty USP units PTE/100 g body wt and 0.2 mg calciferol/100 g body wt administered daily to lactating rats increased milk yield significantly from day 14 to 20 of lactating period, in comparison with controls. PTE increased deoxyribonucleic acid (DNA) content of mammary glands at the end of the experiment. No difference in DNA content of the mammary glands of rats treated with calciferol and Hytakerol was observed. Hytakerol at a dosage of 125 μg/100 g body wt administered daily increased milk secretion significantly only on day 14 of the lactation period, when calcium and phosphorus levels of the blood were about 12 mg/100 ml. It is believed that the effects of PTE, Hytakerol and calciferol in elevation of milk secretion are mediated by increases in the mobilization of serum calcium available to the mammary glands for milk synthesis. (Endocrinology74: 554, 1964)