Evidence for existence of somatostatin-like immunoreactivity with molecular heterogeneity in porcine ovaries.

Measurement of somatostatin (SRIF) by RIA in porcine ovarian tissues after removal of the follicular fluid revealed the existence of immunoreactive (IR) SRIF at concentrations of 2.2 +/- 0.6 ng/g wet weight (mean +/- SD). On gel chromatographic analysis of ovarian extracts one major and two minor components with SRIF-like immunoreactivities have been detected. The major component comprised 59.5 +/- 15.1% of the total IR-SRIF and was coeluted with synthetic tetradecapeptide (SRIF 14). The two other components seemed to have almost the same molecular weights as synthetic octacosapeptide (SRIF 28) (25.1 +/- 10%) and pro-somatostatin (15.4 +/- 5.5%), respectively. It is concluded that SRIF in porcine ovaries is heterogeneous, comprising SRIF 14 as a major component, as well as larger forms of SRIF which probably represent SRIF precursors.