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Journal Article

Covalent linkage of [Phe2,Phe(p-N3)3]AVP to vasopressin receptors

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Fahrenholz,  Falk
Department of Physical Chemistry, Max Planck Institute of Biophysics, Max Planck Society;

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Citation

Eggena, P., Fahrenholz, F., & Schwartz, I. L. (1984). Covalent linkage of [Phe2,Phe(p-N3)3]AVP to vasopressin receptors. American Journal of Physiology: Cell Physiology, 246(5 Pt 1), C486-C493. doi:10.1152/ajpcell.1984.246.5.C486.


Cite as: https://hdl.handle.net/21.11116/0000-0007-DDFB-6
Abstract
We have shown previously ( Eggena et al., Endocrinology 113: 1413-1421, 1983) that [Phe2,Phe(p-N3)3]-AVP induces a prolonged hydrosmotic response in the toad bladder when activated by ultraviolet (UV) light. To determine whether this response is due to covalent binding of the ligand with 8-arginine vasopressin (AVP) receptors, bladders were challenged with the ligand in the presence of AVP or the AVP antagonist, [Phe2,Phe(p-N3)3]AVP, during photolysis. The permeability of bladders to water was tested subsequently in the absence of hormone or analogue. Bladders with a history of exposure to AVP (or to [Phe-(p-N3)2]AVP) during UV irradiation were considerably less permeable to water than controls, suggesting that [Phe2,Phe(p-N3)3]AVP, AVP, and [Phe(p-N3)2]AVP compete for the same receptor system during photolysis. Other experiments were directed at defining optimal conditions for covalent linkage of [Phe2,Phe(p-N3)3]AVP to receptors. These studies have indicated that two 10-min cycles of UV irradiation are more effective than one and that osmotic water flow at a rate of 1 mg X min-1 X cm-2 during irradiation does not interfere with the ligand-receptor interaction. Acidification of the serosal bath solution to pH 6.5 did not inhibit covalent binding of the ligand to receptors during photolysis. However, the capacity of the ligand-receptor complex to increase bladder permeability to water was markedly inhibited by serosal fluid acidification. These experiments have suggested that [Phe2,Phe(p-N3)3]AVP binds covalently to AVP receptors during photolysis and generates a signal that gradually decays as a function of time