Endocrine Abstracts

The cyp19 encodes cytochrome P450aromatase, the key enzyme catalyzing the conversion of androgens to estrogens. Estrogens play a critical role in controlling functional, behavioral and physiological aspects of sexual development both in males and females. Except in Anguilla anguilla, most teleosts studied so far possess two cyp19 genes namely, cyp19a and cyp19b; ovary- and brain-specific respectively. In the present study made in two fishes, Labeo rohita, a major carp and Anabas testudineus, a climbing perch, we found a very high expression of ovary-specific cyp19a mRNA in the ovary of both the fishes. Partial sequencing of cDNA product of cyp19a genes of both the teleosts revealed a high degree of homology with cyp19a cDNA sequences of other teleosts. Comparative seasonal analyses of the expression of cyp19a mRNA and its protein in these two teleosts showed increased expression of this gene in the ovary of vitellogenic and post vitellogenic stages fish. HCG induced a profound stimulatory effect on the expression of ovarian cyp19a mRNA and its protein in both the fishes. Interestingly, cyp19b-specific primers used in semi-quantitative RT-PCR analyses gave ~300bp fragment in the brain of both the fishes. Results showed that cyp19a mRNA expression in the ovary was dependent on the seasonal reproductive variation, however it was not so in the brain. Overlapping expression of cyp19a and cyp19b mRNAs were also detected in ovary and brain of both the teleosts. The physiological and functional significance of the presence of cyp19a and cyp19b in the ovary and brain of these two fishes has been discussed.