Mechanisms of Hyposmotic Volume Regulation in Isolated Nematocytes of the Anthozoan Aiptasia diaphana

Cellular Physiology and Biochemistry

关键词: Aiptasia diaphana;    Nematocytes;    Hyposmotic cell volume regulation;    Potassium channels;    Potassium-chloride cotransport;    Water channels;    N-ethylmaleimide;    Okadaic acid;   

DOI  :  10.1159/000320529

学科分类：分子生物学，细胞生物学和基因

来源: S Karger AG

【 摘 要 】

The nature and role of potassium (K) and water transport mediating hyposmotically-induced regulatory volume decrease (RVD) were studied in nematocytes dissociated with 605 mM thiocyanate from acontia of the Anthozoan Aiptasia diaphana. Cell volume and hence RVD were calculated from the inverse ratios of the cross sectional areas of nematocytes (A/A_o) measured before (A_o) and after (A) challenge with 65% artificial sea water (ASW). To distinguish between K channels and K-Cl cotransport (KCC), external sodium (Na) and chloride (Cl) were replaced by K and nitrate (NO₃), respectively. Inhibitors were added to identify K channels (barium, Ba), and putative kinase (N-ethylmaleimide, NEM) and phosphatase (okadaic acid, OA) regulation of KCC. In 65% NaCl ASW, nematocytes displayed a biphasic change in A/A_o, peaking within 4 min due to osmotic water entry and thereafter declining within 6 min due to RVD. Changing NaCl to KCl or NaNO₃ ASW did not affect the osmotic phase but attenuated RVD, consistent with K channel and KCC mechanisms. Ba (3 mM) inhibited RVD. NEM and OA, applied separately, inhibited the osmotic phase and muted RVD suggesting primary action on water transport (aquaporins). NEM and OA together reduced the peak A/A_o ratio during the osmotic phase whereas RVD was inhibited when OA preceded NEM. Thus, both K channels and KCC partake in the nematocyte RVD, the extent of which is determined by functional thiols and dephosphorylation of putative aquaporins facilitating the preceding osmotic water shifts.

【 授权许可】

CC BY-NC-ND