LIPOPROTEINS AND LIPID-ACCUMULATION WITHIN THE OVARIES OF PENAEID SHRIMP

Phospholipids and triacylglycerols containing saturated and unsaturate d fatty acids were found to accumulate during vitellogenesis in the ov ary of penaeid shrimp, including those of Penaeus semisulcatus. These lipids originate in the food and accumulate in the hepatopancreas on r oute to the ovary. Triacylglycerols, diacylglycerols and phospholipids were found in the high density lipoprotein (HDL) fraction prepared by ultracentrifugation from the hemolymph of vitellogenic females. Triac ylglycerols were not detected in either the HDL of males or that of no n-vitellogenic females. Two lipoproteins were identified in the HDL of vitellogenic females: vitellogenin (Vg) and LP1. The LP1, which is al so found in male HDL, showed one similar to 100 kDa polypeptide in SDS gel electrophoresis, under reducing conditions. The lipids of male an d female HDL were found to carry saturated and polyunsaturated fatty a cids. Vitellin (Vt) is one of the main proteins that accumulate within the ovary during vitellogenesis. Vt was found to dissociate to 2-8 po lypeptides in various penaeid species. In most cases, Vt was isolated in the absence of protease inhibitors, and therefore the subunits repo rted could represent products of protease digestion. The amino acid co mposition is surprisingly similar in four species of Penaeus. Phosphol ipids, triacylglycerols and cholesterol were found to be bound to puri fied Vt of P. semisulcatus, constituting 34.8% of its molecular weight . Accumulating evidence points to intra-ovarian synthesis of Vt. Immun oisolation from cell-free translation of poly(A(+))RNA using antiserum against purified Vt resulted in a 35 kDa polypeptide. Synthesis of cD NA to poly(A(+))RNA that was extracted from vitellogenic ovaries resul ted in a major band of 1-1.1 kb, which was detected by ethidium bromid e staining. Northern analysis of poly(A(+))RNA removed from ovaries an d the hepatopancreas of vitellogenic females resulted in a transcript of 1-1.1 kb. Our results suggest that Vt and Vg are products of one ge ne.