Oxytocin-induced desensitization of the oxytocin receptor☆,☆☆
Section snippets
Cell preparation
Human myometrium was obtained (according to the informed consent procedures that were approved by our institutional committee on human research) from the upper margin of the uterine incision at the time of cesarean delivery. Tissue was handled and dispersed into individual cells in a manner that was published previously.9 Briefly, an initial collagenase digestion was performed to loosen the cells from the connective tissue matrix, and a subsequent digestion was performed to obtain free cells.
Results
Fluorescence experiments that used the calcium-sensitive dye calcium green-1 were performed with a ×40 objective. An average of 50 cells (range, 35-65 cells) were observed for each trial. To determine the percentage of the cells that responded to a given stimuli, every cell in the field was analyzed for rises of intracellular calcium.
Fig 1 shows the experimental protocol and examples of the four types of cells that were observed.
Comment
Understanding factors that control the responsiveness of myometrial cells to oxytocin is clearly important in modern obstetrics. The data we present here are the first to quantitate the loss of the ability of oxytocin to induce intracellular calcium rises as a function of oxytocin pretreatment. We also use an analysis of the distribution of subpopulations of myocytes to yield insight to the mechanism of oxytocin-induced desensitization.
These experiments were performed on cultured cells for
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Supported by the National Institutes of Health, Child Health and Human Development grant No. 1RO1HD 36373.
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Reprint requests: Roger C. Young, MD, PhD, Department of Obstetrics and Gynecology, One Medical Center Dr, Lebanon, NH 03756.