Insulin-related peptide cDNA was characterized in the Pacific oyster Crassostrea gigas. It was determined that three transcripts with differing lengths of 3′-untranslated region (3′-UTR) were expressed in the visceral ganglia. The insulin-related peptide cDNA contained a number of AUUUA motifs that were typical of adenylate/uridylate-rich elements in the 3′-UTR. The deduced preprohormone was a polypeptide of 161 residues and showed a conformation typical of preprohormones of the insulin superfamily, which included conserved amino acids necessary to adopt the globular insulin structure. The expression of the three different transcripts was variable throughout the year, with the highest expression observed in March and lower expression in November and July. The expression of the shortest mRNA in March was about tenfold higher than in July, while the expression of the longest transcript varied approximately twofold during the year. The accumulation of glycogen in the soft body rapidly increased in October and November, and robust body growth and gametogenetic development occurred in March to May. The period of the highest expression of the oyster insulin-related peptide gene corresponded to the onset of body growth and gametogenetic development, but did not overlap with the period of glycogen accumulation. This is the first report that fully details the structure and expression of the insulin-related peptide gene in bivalves.

Arterial rings were prepared from the branchial artery, coeliac artery and ventral aorta of the Japanese dogfish Triakis scyllia and used to determine arterial contraction in a myograph. Noradrenaline caused a dose-dependent contraction (10(-9)-3 x 10(-6) M) that was completely inhibited by pre-treatment with 10(-7) M phentolamine. Homologous dogfish angiotensin II (ANG II) ([Asn1, Pro3, Ile5]-ANG II) also caused dose-dependent contraction (10(-9)-3 x 10(-6) M), but phentolamine had no effect on this response. Administration of dogfish angiotensin I (ANG-I) ([Asn1, Pro3, Ile5, Gln9]-ANG I) resulted in a contraction similar to that produced by ANG II and the effect could be blocked with 10(-7) M captopril. The mammalian ANG II receptor antagonists [Sar1, Ile8]-ANG II and [Sar1, Ala8]-ANG II caused dose-dependent contractions of coeliac artery rings, but were less potent than homologous ANG I and ANG II. These results show that the contractile effect of [Asn1, Pro3, Ile5]-ANG II is not mediated by the alpha-adrenergic system and contractions of arterial rings by noradrenaline and elasmobranch ANG II are mediated by separate vascular receptors. The elasmobranch ANG II vascular receptor may have co-evolved with the unusual structure of this peptide.

Glucose is the main energy substrate in the bovine ovary, and a sufficient supply of it is necessary to sustain the ovarian activity. Glucose cannot permeate the plasma membrane, and its uptake is mediated by a number of glucose transporters (GLUT). In the present study, we investigated the gene expression of GLUT1, 3 and 4 in the bovine follicle and corpus luteum (CL). Ovaries were obtained from Holstein × Japanese Black F1 heifers. Granulosa cells and theca interna layers were harvested from follicles classified into five categories by their physiologic status: follicular size (≥ 8.5 mm: dominant; < 8.5 mm: subordinate), ratio of estradiol (E₂) to progesterone in follicular fluid (≥ 1: E₂ active;<1: E₂ inactive), and stage of estrous cycle (luteal phase, follicular phase). CL were also classified by the stage of estrous cycle. Expression levels of GLUT1, 3 and 4 mRNA were quantified by a real-time PCR. The mRNA for GLUT1 and 3 were detected in the bovine follicle and CL at comparable levels to those in classic GLUT-expressing organs such as brain and heart. Much lower but appreciable levels of GLUT4 were also detected in these tissues. The gene expression of these GLUT showed tissue- and stage-specific patterns. Despite considerable differences in physiologic conditions, similar levels of GLUT1, 3 and 4 mRNA were expressed in subordinate follicles as well as dominant E₂-active follicles in both luteal and follicular phases, whereas a notable increase in the gene expression of these GLUT was observed in dominant E₂-inactive follicles undergoing the atretic process. In these follicles, highly significant negative correlations were observed between the concentrations of glucose in follicular fluid and the levels of GLUT1 and 3 mRNA in granulosa cells, implying that the local glucose environment affects glucose uptake of follicles. These results indicate that GLUT1 and 3 act as major transporters of glucose while GLUT4 may play a supporting role in the bovine follicle and CL.