Canine reproduction: effects of a single injection of medroxyprogesterone acetate on the reproductive organs of the bitch.

Abstract

A study was undertaken to determine the effects of medroxyprogesterone acetate (MAP) on the reproductive organs of the bitch 1) at different intervals after injection 2) at different stages of the estrous cycle and 3) at different ages. A total of 150 purebred Beagle bitches were allotted to experimental groups. 100 bitches were given 50 mg of MAP subcutaniously on the medial aspect of the right thigh and 50 bitches were used as nontreated controls. The stage of estrous was determined. Serial uterine biopsies and necropsies were performed. Alterations were not seen in the adrenal glands pituitary gland or ovaries that could be attributed to the treatment. The most marked changes were seen in the uterus. Treatment with MAP resulted in a stimulation of the endometrium in 20.9% of the bitches. The most noticeable effects occurred at postinjection Day 20 and in bitches more than 5 years old at the time of treatment. Morphologic alterations of the uterus referred to as the corkscrew effect were related to the endogenous or exogenous progestational influence. The corkscrew uterus occurred in 56% of the treated bitches.