ACROSIN INHIBITOR BSTI-I IN SEMINAL AND OR BLOOD-PLASMA OF MALE AND FEMALE PIGS UNDER DIFFERENT REPRODUCTIVE CONDITIONS/

Boar seminal plasma trypsin-acrosin inhibitor I (BSTI-I) concentration s were measured by homologous radio-immunoassay: 1. In seminal and blo od plasma of boars, before and after castration and following testoste rone propionate administration (after castration); 2. In blood plasma of gilts, during the oestrous cycle and following insemination; and 3. In blood plasma of sows at the time of weaning. Firstly, it was demon strated that the blood-plasma component, measured by the radio-immunoa ssay, is indeed BSTI-I. The main goal of the study was to determine BS TI-I concentrations during different reproductive stages and to evalua te the possibilities for using these measurements in fertility studies . In boars, BSTI-I levels were testosterone dependent, in both the sem inal plasma and circulation, as shown by their response to castration and testosterone propionate administration. The blood-plasma BSTI-I le vel appeared to be sex dependent. in all animals measured so far, the lowest concentration measured in a group of non-castrated males was 1. 5 times the highest concentration measured in a group of non-inseminat ed females. Between females, considerable differences in the endogenou s blood-plasma BSTI-I level were observed. In gilts, the endogenous bl ood-plasma BSTI-I concentration showed no clear relationship with the phase of the oestrous cycle. In sows, a highly significant increase in the BSTI-I concentration was found during a 5-day period following we aning. After insemination, the seminal plasma BSTI-I was found to be a bsorbed and could be detected in the circulation. The highest blood-pl asma levels of this exogenous BSTI-I were reached at about 4 h after i nsemination. Absorption of seminal-plasma BSTI-I varied during the per iod of oestrus; however, no relationship between blood-plasma BSTI-I c oncentrations and the fertilization rate and embryonic survival could be demonstrated. The results presented here do not reveal indications that BSTI-I measurements in blood plasma can be used as a parameter in fertility studies.