Vasoactive intestinal polypeptide and calcitonin gene-related peptide in the developing rat heart atria

Vasoactive intestinal polypeptide-like immunoreactivity (VIP-LI) and calcit onin gene-related peptide (CGRP)-LI concentrations were determined in the d eveloping rat heart atria using radioimmunoassay. Peptide levels were analy sed on postnatal days 1, 10, 25, 45, 60, and 85 (P1-P85) separately in the right (RA) and left atria (LA). No sex differences were revealed at any age examined. VIP-LI has been already detected in both atria at P1 in concentr ations comparable to values at P10. In the RA, VTP-LI levels increased sign ificantly between days P10 and P25. remained high at P45 and then declined. In the LA, VIP-LI concentrations did not differ from those in the RA on da ys P1, P10, P25, and P45. However, regional differences were found at P60 a nd P85, when the peptide levels were significantly higher in the LA than in the RA. The postnatal changes in CGRP-LI concentrations were comparable in both atria with similar values at P1 and P85. After birth, CGRP levels dec reased gradually till P45, then they increased till P60 and declined again at P85. The results demonstrate that there is an asymmetry in the postnatal development of the atrial VIP-LI and CGRP-LI concentrations. VIP-LI levels reached their maximum at P25, whereas CGRP-LI levels at P60. Relatively hi gh peptide concentrations in neonatal atria and their variations during dev elopment might be related to diverse trophic functions of VIP and CGRP. (C) 2000 Elsevier Science B.V. All rights reserved.