Effect of cyproterone acetate, levonorgestrel and progesterone on adrenal glands and reproductive organs in the beagle bitch.

The effects of short-term (8 weeks) treatment with different doses of cyproterone acetate (CPA), levonorgestrel (LN) and progesterone (PRO) on the adrenal gland, ovary, uterus and vagina were studied in cycle-synchronised beagle bitches (first anoestrus). The same organs from non-treated primiparous beagle bitches at the 6th and 9th weeks of pregnancy were also included. In the animals treated with the highest doses of CPA (4.0 mg/kg/day orally) and PRO (42.5 mg/kg/day subcutaneously), as well as in pregnant bitches (9th week of pregnancy), a decrease in adrenal weight and cortex width and also an apparent loss of cells in the zona fasciculata and zona reticularis were observed. A marked increase in ovarian weight was recorded only in pregnant bitches (6th week of pregnancy). This was reflected by the presence of multiple well-developed corpora lutea. The ovaries of virgin control and progestagen-treated bitches revealed ovarian atrophy. Progestagen treatment caused marked stimulation of the uterus, resulting in dose-related oedematous and hyperplastic changes. Comparable findings were also observed during pregnancy. The vaginal epithelium of the progestagen-treated and pregnant bitches showed marked mucification as compared with control bitches. These structural responses indicate that progestagen treatment stimulates a pseudopregnancy-like condition in the adrenal glands, uterus and vagina of the beagle bitch.