Effects of a synthetic prostaglandin analogue, cloprostenol, on the corpus luteum of the guinea pig.

The effects of a synthetic prostaglandin analogue, cloprostenol, on luteal function in the guinea pig were studied. At a dose of 250 micrograms, cloprostenol administered I-P on day 9 of the cestrous cycle caused a reduction in the length of the oestrous cycle from 17.4 +/- s.d.0.9 to 14.5 +/- 1.1 days (p less than 0.01). Lower doses were ineffective, and post-treatment cycles were not different in length from pre-treatment cycles. Cloprostenol also caused a dose-dependent reduction in luteal weight, which fell from 3.52 +/- 0.82 to 1.82 +/- 0.41mg (p less than 0.01) 48 h after administration of a 250 micrograms dose on day 9. Plasma progesterone, measured by radioimmunoassay, was reduced from 4.67 +/- 0.59 to 2.69 +/- 0.66 ng ml-1 (p less than 0.01) 48 h after administration of 250 micrograms cloprostenol on day 9. 250 micrograms cloprostenol also reduced blood flow per corpus luteum, measured by 85Sr-labelled 15 microns microspheres, both at 3 h (20.20 +/- 10.36 to 9.40 +/- 4.20 microliters min-1; p less than 0.05) and at 48 h (18.47 +/- 8.27 to 5.23 +/- 1.90 microliters min-1; p less than 0.01) after administration on day 9. No adverse side-effects were observed at any dose level of cloprostenol used. It was concluded that cloprostenol is a useful experimental luteolysin in the guinea pig.