G. GEIER, U. HOEGER, Institut für Zoologie der Universität Mainz, Saarstr. 21, D - 6500 Mainz
| Uptake of inosine and guanosine was measured in male germ cells of the polychaete N. virens at different stages of development. In spermatogonia I (spg I) and spermatid stages, total inosine uptake at 12°C and ambient concentrations of 100 µmol/l was relatively low (10-50 nmol *ml of packed cell volume (pcv) -1 * h-1). A rapid increase (150-300 nmol*ml of pcv-1 * h-1) was found during transition from spg I to spg II with a subsequent decline to low values (10-30 nmoles * ml of pcv-1 * h-1) in spermatocyte and spermatid stages. This transient increase may be related to the proliferative activity of spg I stages leading to spg II stages, which increases the demand of purine precursors for nucleic acid synthesis. inosine uptake of spermatozoa stages was extremely variable and high uptake rates (10-300 nmoles * ml of pcv-1 * h-1) were found in some, but not in all cases. In all stages, the uptake rates for guanosine remained at a lower levels (below 75 nmoles * ml of pcv-1 * h-1) and no clear stage specific pattern was evident except for low values (< 10 nmoles * ml of pcv-1 * h-1) in motile spermatozoa. | For both nucleosides, two uptake components were identified: a linear uptake up to concentrations in the medium of 300 µmol/l and a saturable component (app. km: 9-60 µmol/l) which was inhibited by iodoacetamide suggesting the presence of an facilitated transport mechanism. The presence of the two uptake components was related to the stage of gamete development: the saturable uptake component present in early spg I changed to a linear uptake in late spg I. In spg II stages, both uptake components were present while in spermatocytes, only the saturable component was present. Spermatids and early spermatozoa showed only a linear uptake. In the coelomic fluid, guanosine (0.5-20 µmol/l) and inosine (> 3 µmol/l) were the main nucleosides; during spg II and spermatocyte stages, inosine reached high concentrations (100-1000 µmol/l). |
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