Smooth muscle cells were isolated from estrogenized rat myometrium by collagenase digestion. Electron microscopic examination and measurement of cell lengths by image-splitting micrometry were carried out after fixation with acrolein. Mean lengths of cells before and after isolation were 81.7 and 66.9 micron, respectively. Responses of cells were compared with contractions of isolated strips recorded isometrically. Effects of carbachol and KCl were examined in 2 mM Ca, 2 mM Ca + 4 mM EGTA, and 2 mM Ca + 10(-8) M nitrendipine solution. Carbachol and KCl produced concentration-dependent shortening of isolated cells maximal at 30 s after addition. The concentrations of carbachol required to produce shortenings were about 100-fold less than those required to produce isometric contractions; but no major difference was observed in the concentration dependence of cell shortening and isometric contraction produced by potassium-induced depolarization. In 2 mM Ca solution, there was a phasic response, followed by a tonic response such that more than 50% of maximum cell shortening was maintained for 10 min. However, in 2 mM Ca + 4 mM EGTA or 10(-8) M nitrendipine, the tonic contraction was abolished and cells rapidly relaxed after 30 s. If carbachol was added to cells after varying times in the EGTA-containing solution, the ability to initiate a contraction declined exponentially with a half-time of 160 s. Effects of depolarization by KCl were examined in 2 mM Ca plus nitrendipine and 2 mM Ca + 4 mM EGTA solution. Shortening occurred in 2 mM Ca solution by depolarization but not if nitrendipine was added. Though shortening was not observed in 2 mM Ca + 4 mM EGTA solution by KCl, subsequent addition of carbachol induced shortening. These results suggested that there was an intracellular Ca store site from which Ca was released by carbachol and which was not affected by depolarization in the absence of external Ca. No evidence was obtained that the contraction persists in Ca2+-free medium in isolated cells, which is in agreement with previous findings in small muscle strips in which only a similar transient response was obtained.

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The properties of Ca2+ channels in strips and single muscle cells of longitudinal muscle of estrogen-dominated rat myometrium were studied under the effects of elevation of K+ concentration, the partial channel agonist Bay K 8644, and nitrendipine. In isolated strips in 0.5 mM Ca2+, Bay K 8644 (pD2 = 7.8-8.0) lowered the threshold for and enhanced the contractions in response to an elevation of K+ concentration, including the maximum response to K+ elevation alone. Bay K 8644 alone in concentrations up through 10(-6) M did not initiate contractions in 0.5 mM Ca2+ solutions. At higher concentrations (10(-5) M), Bay K 8644 behaved as an antagonist to contractions induced by elevation of K+. In isolated cells 10(-7) M Bay K 8644 enhanced the shortenings to elevated K+ and lowered the threshold K+ concentration required. Also no significant contraction occurred with 10(-7) M Bay K 8644 at normal K+ concentration. In contrast with its effect in isolated strips, no significant increase in maximum shortening (to 60 mM K+) was observed, possibly because cells without a mechanical load were maximally shortened by K+ alone. From these studies, we conclude that Ca2+ channels of isolated strips and cells of rat myometrium behave similarly and have similar properties to those of other smooth muscles in their interactions with elevation of K+, nitrendipine, and Bay K 8644.

A case of endometrial cancer, detected and treated 2 years and 7 months after childbirth, is reported.The patient was born in 1948. After a spontaneous delivery in January of 1979, endometrial carcinoma was detected in August of 1981.There was no history of pill usage or menstrual cycle irregularities. No associated illnesses, such as diabetes mellitus, obesity, or hypertension, were present.Preoperative determination of hormone levels did not indicate any marked abnormalities.Histologically, the lesion was a mixed adenosquamous carcinoma with no invasion of the myometrium.

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