Abstract
To assess a possible direct tubular action of α-human atrial natriuretic peptide (α-hANP), we studied the effects of α-hANP on volume reabsorption (JV), transepithelial voltage (VT), and p-aminohippuric acid (PAH) secretion in the rabbit proximal straight tubules (PST) by in vitro microperfusion technique. In superficial PST (SFPST), addition of α-hANP at various concentrations (10-7, 10-9, 10-11M) to the bath solution did not alter JV significantly. Bath α-hANP (10-7M) did not change VT in SFPST, either. In juxtamedullary PST (JMPST), addition of α-hANP (10-7M) to the bath solution changed neither VT nor JV significantly. The α-hANP (10-7M) in the luminal fluid caused no changes in either VT or JV in SFPST. Furthermore, α-hANP (10-7M) in the bath did not change the rate of PAH secretion in SFPST. Thus, we could not obtain any evidence for direct tubular action of α-hANP in rabbit PST. Accordingly, α-hANP may increase solute excretion without directly affecting solutes transport in PST of the rabbit kidney.
