# STEROID-INITIATED EXOCYTOSIS IN SPERM

> **NIH NIH R01** · UNIVERSITY OF CALIFORNIA AT DAVIS · 1994 · $173,595

## Abstract

The acrosome reaction (AR) is a central event of mammalian fertilization
involving the fusion and fenestration of sperm head membranes. The
molecular events that initiate this exocytotic process are not completely
understood. The goal of this research is to increase our knowledge of those
events in human sperm. These studies will be carried out with an in vitro
human sperm incubation system. My laboratory has found that progesterone, a
steroid hormone present in follicular fluid and secreted by granulosa cells
and cells of the cumulus oophorus, can initiate the human sperm AR by
increasing sperm [Ca2+]. This is of particular interest because: 1) sperm
have to pass through the cumulus extracellular matrix during in vivo human
fertilization; 2) the [Ca2+] increase is so fast (< 1 min) that a sperm
steroid surface receptor may be involved.

These studies will include: 1) whether steroids increase [Ca2+] in the
human sperm head; 2) determination of the steroid structure necessary for
the increase in [Ca2+] and the AR; 3) experiments to help determine whether
or not there is a plasma membrane steroid receptor; 4) investigation of the
possible role of steroid inhibition of Na+, K+ -ATPase and [Ca2+ + Mg2+]
-ATPase in increasing sperm head [Ca2+] and thereby the AR.

Methods to be used include: in vitro incubation of human sperm,
computerized fluorescence image analysis, transmission electron
microscopy,immunofluorescent assay of the AR,
HPLC, (45)Ca-efflux studies and ATPase assays with (32)P-substrate.

It is hoped that these studies will result in a greater understanding of
the molecular basis of human fertilization and thereby lead in the future
to new methods of contraception and of treatment for infertility. In
addition, the increasing of intracellular [Ca2+] by a steroid via a cell
surface-mediated mechanism might have relevance to Ca2+-requiring events in
somatic cells. Thus, these studies may also be of importance outside the
field of fertilization.

## Key facts

- **NIH application ID:** 2198764
- **Project number:** 5R01HD023098-05
- **Recipient organization:** UNIVERSITY OF CALIFORNIA AT DAVIS
- **SAM.gov UEI:** TX2DAGQPENZ5
- **Principal Investigator:** STANLEY MEIZEL
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 1994
- **Award amount:** $173,595
- **Award type:** 5
- **Project period:** 1990-08-01 → 1995-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/2198764

## Citation

> US National Institutes of Health, RePORTER application 2198764, STEROID-INITIATED EXOCYTOSIS IN SPERM (5R01HD023098-05). Retrieved via MORVS 2026-10-25 from https://api.morvs.ai/grant/nih/2198764. Licensed CC0.

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