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Localisation of inositol trisphosphate and ryanodine receptors during mouse spermatogenesis: possible functional implications

Published online by Cambridge University Press:  05 April 2001

Claudia L. Treviño
Affiliation:
Depto. Genética y Fisiología Molecular, Instituto de Biotecnolog'a-UNAM, Apdo. Postal 510-3, Cuernavaca, Morelos 62250, Mexico
Celia M. Santi
Affiliation:
Depto. Genética y Fisiología Molecular, Instituto de Biotecnolog'a-UNAM, Apdo. Postal 510-3, Cuernavaca, Morelos 62250, Mexico Depto. Biofísica, Instituto de Fisiología Celular-UNAM, Mexico City, Mexico
Carmen Beltrán
Affiliation:
Depto. Genética y Fisiología Molecular, Instituto de Biotecnolog'a-UNAM, Apdo. Postal 510-3, Cuernavaca, Morelos 62250, Mexico
Arturo Hernández-Cruz
Affiliation:
Depto. Biofísica, Instituto de Fisiología Celular-UNAM, Mexico City, Mexico
Alberto Darszon
Affiliation:
Depto. Genética y Fisiología Molecular, Instituto de Biotecnolog'a-UNAM, Apdo. Postal 510-3, Cuernavaca, Morelos 62250, Mexico
Hilda Lomeli
Affiliation:
Depto. Genética y Fisiología Molecular, Instituto de Biotecnolog'a-UNAM, Apdo. Postal 510-3, Cuernavaca, Morelos 62250, Mexico

Abstract

During spermatogenesis the activity of intracellular Ca2+-release channels is likely to play an important role in different specific cellular functions. Accordingly, messenger RNAs for the three inositol 1,4,5-trisphosphate receptor (IP3R) subtypes were found to be present throughout spermatogenesis. Immunocytochemical analysis revealed distinct distribution patterns of the mature IP3Rs during sperm differentiation. At early stages, IP3Rs are distributed throughout the cytoplasm, and as differentiation proceeds they become selectively localised to the Golgi complex. Consistently, spermatogonia underwent large intracellular Ca2+ release in response to thapsigargin (TG), while smaller responses were detected in late spermatocytes and spermatids. The distribution of IP3Rs and the larger Ca2+-release responses found in spermatogonia, suggest that IP3Rs may be involved in cell proliferation at this stage. This notion is supported by our observations in a spermatogenic cell line that depletion of intracellular Ca2+ pools using TG inhibits cell division, and that incubation with an IP3R-I antisense oligonucleotide completely inhibited proliferation. Furthermore, the three genes encoding ryanodine receptor proteins (RyRs) are expressed at all stages of spermatogenesis. However, immunocytochemical studies with specific antibodies against each of the RyR subtypes detected types 1 and 3 in spermatogenic cells and only type 3 in mature sperm. In contrast to IP3Rs, RyRs remain scattered in the cytoplasm throughout differentiation. Functional responses to caffeine and ryanodine were absent in spermatogenic cells and in mature sperm. These findings suggest that IP3Rs have significantly more important roles in spermatogenesis than RyRs, and that one of these roles is crucial for cell proliferation.

Type
Research Article
Copyright
1998 Cambridge University Press

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