The effect of glucagon on spontaneous contractility of isolated pregnant uterine muscle.
OBJECTIVE
To determine whether glucagon has relaxant effects on the spontaneous contractions of term pregnant human uterine smooth muscle in an isolated preparation.


METHODS
Myometrial specimens were excised from the upper incisional surface of the lower uterine segment in seven women during elective cesarean delivery. The muscle strips were suspended in tissue baths and isometric tension was recorded. After establishing rhythmic spontaneous contractions, glucagon reconstituted with distilled water or the accompanying diluent was added directly to the bath in a cumulative manner. In the second phase of the study, the effect of the diluent (1.6% glycerin with 0.2% phenol) alone on muscle contractility was evaluated.


RESULTS
Glucagon had no effect on uterine muscle concentrations when reconstituted with distilled water. However, glucagon reconstituted with the diluent decreased the contractile amplitude by 27 +/- 11% (mean +/- standard deviation, P < .01) and the frequency by 13 +/- 10% (P < .05) at a concentration of 20 micrograms/mL. At a cumulative concentration of 40 micrograms/mL, the reductions in amplitude and frequency were 65 +/- 13% (P < .001) and 18 +/- 14% (P < .01), respectively. The diluent at equivalent concentrations exerted relaxation similar to that produced by glucagon when reconstituted with the diluent. The relaxant effects were not different between the two solutions (P > .2, power 90%, alpha = .05).


CONCLUSIONS
These results suggest that relaxation of contractions was likely caused by the diluent rather than by glucagon. We conclude that glucagon does not have a direct relaxant effect on spontaneous contraction of isolated uterine muscle obtained from term pregnant uteri.
Shin
Y K
YK
Department of Anesthesia, School of Medicine, Georgetown University, Washington, DC 20007, USA.
Collea
J V
JV
Kim
Y D
YD
D000328:Adult; D005260:Female; D005934:Glucagon / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects*; D009126:Muscle Relaxation / Q000187:drug effects; D009465:Neuromuscular Agents / Q000494:pharmacology; D011247:Pregnancy; D013565:Sympatholytics / Q000494:pharmacology*; D014590:Uterine Contraction / Q000187:drug effects; D014599:Uterus / Q000187:drug effects*
D009465:Neuromuscular Agents; D013565:Sympatholytics; D005934:Glucagon