The opercular epithelium of the teleost, Fundulus heteroclitus, is unique with respect to other Cl secreting epithelia in that the rate of Cl transport is antagonistically regulated by catecholamines. Activation of the α-adrenergic receptors by arterenol inhibits the transport rate, while activation of the β-adrenergic receptors by isoproterenol stimulates the transport rate (Degnan and Zadunaisky, 1979). In the present study, specific adrenergic agonists and antagonists were employed to further characterize the nature of the receptors involved in these control mechanisms, α1-agonists had no effect on the transport rate, while α2-agonists produced an inhibition indistinguishable from that of arterenol. Furthermore, this inhibition was unaffected by α1-agonists and blocked by α2-agonists. None of the specific β1- or β2-agonists produced a significant stimulation of the transport rate when compared to isoproterenol. However, the stimulatory effect of isoproterenol was unaffected by β2-antagonists, and blocked by β1-antagonists. These findings demonstrate that the inhibitory effect of catecholamines on Cl transport in the opercular epithelium is mediated solely by the α2-adrenergic receptors, while the stimulatory effect is mediated solely by the β1-adrenergic receptors.
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
- Animal Science and Zoology