[Alteration of endothelin-1 receptor in the choroid plexus of rats with kaolin-induced experimental hydrocephalus]

Abstract

Specific binding sites for endothelin-1 (ET-1) in the choroid plexus of rats with kaolin-induced hydrocephalus were analyzed using quantitative receptor autoradiographic technique with 125I-ET-1. Unlabeled ET-1 and its natural analog ET-3 inhibited the binding of 125I-ET-1 to the choroid plexus of control rats with similar high potencies. However, possibly related substances, such as ion channel regulators (omega-conotoxin GVIA, nitrendipine, verapamil, diltiazem, alpha-bungatmtoxin, aconitine, apamin), ouabain and atrial natriuretic peptide did not affect the binding. Scatchard analysis revealed the presence of a single class and high affinity binding sites for ET-1 in the choroid plexus. The number of 125I-ET-1 binding sites in the choroid plexus of rats with kaolininduced hydrocephalus was significantly lower, when compared with those in the age-matched control rats; maximum number of binding sites (Bmax) was 16.3 +/- 0.6 and 36.2 +/- 2.5 fmol/mg, respectively (p less than 0.01, n = 5). There was no significant difference in the binding affinities; affinity constants (Ka) was 2.6 +/- 0.3 x 10(9) M in control rats and 3.5 +/- 0.5 x 10(9) in hydrocephalic rats (n = 5). These results suggest that ET receptors may play a role in the regulation of cerebrospinal fluid production.