Year: 2017
Type: dissertation
Abstract: Ca\\(^{2+}\\) signals from activated Ca\\(^{2+}\\) channels (CatSper) and mobilisation of Ca\\(^{2+}\\) stores regulate human sperm cell behaviour as they ascend the female tract. I investigated the effects on human sperm [Ca\\(^{2+}\\)]i and behaviour of CatSper channel activation (alkaline pH and progesterone) and Ca2+-store mobilisation (4-aminopyridine, thimerosal) using a fluorescence plate reader and CASA. Extracellular alkalinisation raised pH¬i (pHi = 6.9 and 7.2 at pHo7.4 and 8.5 respectively), caused tonic elevation of [Ca\\(^{2+}\\)]i, which was partially inhibited by CatSper block and increased the proportion of hyperactivated cells (from 1.8±0.5 to 10.5±1.6%; n=34, P=1x10\\(^{-7}\\)). Progesterone elevated [Ca\\(^{2+}\\)]i but caused negligible hyperactivation. Co-application of these stimuli revealed little, if any, synergistic interaction. Ca\\(^{2+}\\)-store mobilisation (4-aminopyridine) caused prolonged [Ca\\(^{2+}\\)]i elevation and was associated with strong hyperactivation. Analysis of [Ca\\(^{2+}\\)]i and hyperactivation data from 24 different conditions in this study showed a continuous relationship between [Ca\\(^{2+}\\)]i and hyperactivation. The strong hyperactivating effect of store mobilisation (compared to CatSper activation) may reflect opening of store-operated channels. Human sperm behaviour assessed over a 180 s recording revealed regular ‘switching’ between progressive and various hyperactivated types. Mobilisation of Ca\\(^{2+}\\) stores potently increased hyperactivated behaviour and suppressed the rate of behavioural switching.
Author: Cosmas Ezekaibeya Achikanu
Language: English
Subfield: Reproductive Medicine
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W2784740133