Localization and age-dependent expression of the inward rectifier K+ channel subunit Kir 5.1 in a mammalian reproductive system

Kir 5.1 is a member of the inward rectifier potassium channel superfamily w hich does not form functional channels when expressed by itself in Xenopus laevis oocytes. rt-PCR reveals high levels of Kir 5.1 mRNA expression in te stis but the function of this channel remains unknown, To determine the cel l-specific expression of this channel in the testis ne raised a polyclonal antibody against an external epitope of Kir 5.1 and tested its specificity in Xenopus oocytes expressing several cloned Kir subunits, Strong immunorea ctivity for Kir 5.1 was found in seminiferous tubules of rat testis and, pa rticularly, in spermatogonia, primary and secondary spermatocytes, spermati ds and in the head and body of spermatozoa, The intensity of Kir 5.1 immuno fluorescence. quantified using laser scanning microscopy, increased with ag e at every stage in the development of sperm from spermatogonia and reached a peak in 60-day-old rats. In contrast. the immunofluorescence decreased i n 90-day-old animals and was detected mostly in spermatozoa. The results de monstrate that Kir 5.1 expression in the testis is localised to cells invol ved in spermatogenesis, showing a temporal pattern of expression during sex ual maturity, (C) 1999 Federation of European Biochemical Societies.