Low energy charge in human uterine muscle.

Six pregnant and 10 non-pregnant patients undergoing Caesarean section and laparatomy, respectively participated in this study which was aimed at determining the energy status of human uterine muscle and comparing it to that of striated muscle from the same individual. Biopsies were taken from the fundus uteri between the ligamenta rotunda and from the rectus abdominis muscle. A low energy charge of 0.55 in pregnant patients and 0.64 in non-pregnant patients was observed in uterine biopsies, compared to the expected value of 0.90 found in rectus biopsies. The main determinant of this finding was a 4-8 times lower level of ATP in uterine biopsies compared to that in rectus biopsies. The same pattern was apparent for total nucleotide content and creatine phosphate. The ADP and AMP contents were of the same order of magnitude in both tissues. The lactate content in uterine biopsies from pregnant patients was significantly higher than that found in biopsies from rectus muscle and from uterine tissue of non-pregnant patients, indicating an increased glycogenolysis in pregnant uterus. The low energy charge and low level of phospho-compounds observed in uterine muscle, regardless of the functional state, are new and unexpected findings.