Characteristics and specific localization of receptors for atrial natriuretic peptides at non-neuronal cells in cultured mouse spinal cord cells

Abstract

Characteristics of atrial natriuretic peptide receptors were determined in cultured mouse spinal cord cells. Saturation and competition experiments demonstrated the presence of a single class of atrial natriuretic peptide binding sites with high affinity (K D = 0.054 nM) and a density of 1.92 fmoles/10 6 cells. A similar affinity (K D = 0.070 nM) was observed in rat spinal cord membrane preparations. These atrial natriuretic peptide binding sites were functional receptors since the treatment of cells with atrial natriuretic peptide increased cyclic guanosine monophosphate levels within these cells in a classical time-dependent manner. When atrial natriuretic peptide was applied onto the cell body of intracellularly recorded spinal cord neurons, this peptide did not evoke a change of the input resistance or of the resting membrane potential value. Light-microscopic autoradiography studies showed that no atrial natriuretic peptide binding could be detected on typical birefringent neurons but it could be located on astroglial and epithelial cells as identified by immunocytochemical markers. These results show that functional atrial natriuretic peptide receptors with high affinity exist in cultured mouse spinal cord cells and are not located on neurons. The presence of atrial natriuretic peptide receptors on astrocytes suggests that this neuropeptide might be a good candidate for neuron-glial communication. As the atrial natriuretic peptide binding sites previously shown in epithelia responsible for maintaining fluid and electrolyte gradients, the atrial natriuretic peptide receptors on epithelial cells in these spinal cord cultures may be involved in vivo in the control of water balance in the central nervous system.