Lipids during Bufo arenarum oogenesis

Abstract

The content and composition of phospholipids and triacylglycerols (TAGs) in Bufo arenarum oocytes in stages III and IV of their oogenesis were studied. The total amount of phospholipids in stage IV oocytes is 0.5-fold higher than in stage III oocytes. In both cases, the main phospholipids are phosphatidylcholine (PC) and phosphatidylethanolamine (PE). A striking observation concerns the high level of diphosphatidylglycerol (DPG) in stage III oocytes, which could be indicative of a relatively larger mitochondrial population with respect to other oogenetic stages. A net increase in sphingomyelin content was found during oogenesis. This fact could be related to the role of this phospholipid in the signal transductional pathways. In PC, palmitic (16:0), linoleic (18:2) and oleic (18:1) are the major fatty acids for both types of oocytes, while in PE the main acyl groups are 18:1, 16:0, arachidonic acid (20:4n6) and 18:2. PE is more unsaturated than PC and both phospholipids are more unsaturated in stage III oocytes than in stage IV oocytes. The amount of triacylglycerols is 0.3-fold higher in stage IV oocytes than in stage III oocytes. In both stages, the main fatty acids are 18:2, 18:1 and 16:0. During oogenesis, a significant increase in 18:1 and 18:3n3, and a decrease in 18:2 of TAG were found. The unsaturation index of TAGs from stage IV oocytes is higher than that from stage III oocytes. The TAG increase during oogenesis is consistent with the putative use of these lipids as a source of energy in embryo development.

Mitochondrial lipids in Bufo arenarum full-grown oocytes

“…Similar levels of 16:1 and linolenic acid (18:3) were found. The fatty acid profile is similar to that observed in TAG from stage III oocytes (Valdéz Toledo & Pisanó, 1980), in which a relatively larger mitochondrial population with respect to other oogenetic stages has been reported (Bruzzone et al, 2003). In DAG, 16:0 is the main fatty acid followed by 18:1, 18:2, 18:0 and 16:1.…”

“…Mitochondria are accumulated and aggregated during the previtellogenic period as a mitochondrial cloud and are dispersed throughout the cytoplasm during vitellogenesis (Balinsky & Devis, 1963;Van Blerkom & Runner, 1984). Similarly, a recent study in Bufo arenarum oogenesis has demonstrated that the relative mitochondrial population of stage III oocytes (late vitellogenesis) is larger than that of stage V (Bruzzone et al, 2003). In Xenopus, their level remains constant through maturation, fertilization and early development (Webb & Smith, 1977;Callen et al, 1980).…”

Single embryo and oocyte lipid fingerprinting by mass spectrometry

“…Nonetheless, membrane PC and SM changes and their roles during embryo development have not been reported. Changes in lipid patterns during oocyte development have been observed in Bufo arenarum oogenesis and early embryo development ( 39,40 ). Although used as a model for understanding oogenesis and embryogenesis, due to their high numbers of gametes and external fecundation, frog reproduction differs signifi cantly from that of mammalians species.…”