Changes in plasma kininogen levels in rats before ovulation, and after treatment with luteinizing hormone and oestradiol-17β

Abstract

Abstract. The pre-ovulatory fall in plasma kininogens in rats with 4 day oestrous cycles started between 12.00 and 15.00 h pro-oestrus, reached a maximum decline of 51% by 18.00 h pro-oestrus, and started to recover before ovulation. Because these changes appeared to correspond with the LH-surge, and to follow the peak in plasma oestradiol-17β levels, both of these hormones were tested for possible effects on plasma kininogens. Intracardiac injections of 110 IU of equine LH into dioestrous rats were followed by a decline of 30.8 ± 6.7% in plasma kininogens, 6 h after injection (significant, P< 0.01). Values were still depressed, but recovering, 12 h after treatment; the reduction was 21.3 ± 5.8% (significant, P < 0.01). Controls showed no decline. Injections of oestradiol-17β (1.0 μg/100 g body weight) produced no significant effects. It is suggested that the LH surge may be responsible, at least in part, for the decline in plasma kininogens seen before ovulation.