31P NMR studies of adenosine-stimulated ATP synthesis in perfused luteinized ovaries

31P NMR studies of phosphate metabolism in the ovulatory process induced by gonadotropins in perfused rabbit ovary

The concentrations of phosphate metabolites were measured in perfused rabbit ovaries before, during and after ischemia, and during the ovulatory process induced by the administration of pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (HCG) using 31P NMR spectroscopy. A decrease in adenosine triphosphate (ATP) and an increase in inorganic phosphate (Pi) during ischemia were observed. After reperfusion of the ovary, both ATP and Pi levels returned to their initial control levels. These results are in agreement with the results observed in other organ tissues. On the other hand, ATP levels rapidly decreased dose dependently with infusion of HCG during 10 h of perfusion. A decrease in ovarian ATP concentration after infusion of HCG was also confirmed by enzymatic analysis of the extracts from ovarian tissues. On the other hand, significant changes in Pi levels were not observed throughout the perfusion period. Furthermore, significant changes in phosphomonoester (PME) levels, adenosine diphosphate (ADP) levels and intracellular pH were not observed before and during the infusion of HCG. The concentration of cyclic adenosine 3',5'-monophosphate (cAMP) in the perfusate after the perfusion was also measured during the ovulatory period. Within 30 min cAMP significantly increased dose dependently and reached peak levels within 60 min. The concentration of cAMP then gradually decreased. Ovulatory efficacy during the infusion of HCG was also observed. These results suggest that the decreased ATP in the successive processes leading to ovulation probably reflects protein phosphorylation through the activation of the cAMP-dependent protein kinases prior to induction of various chemical reactions related to the initiation of ovulation.

13C NMR kinetic studies of the rapid stimulation of glucose metabolism by estrogen in immature rat uterus

Glucose metabolism in control and estrogen stimulated rat uteri was investigated using 13C NMR spectroscopy. By employing an NMR adapted perifusion system, and developing protocols and methods based on the application of [1-13C]glucose labeling, it was possible to measure, with a temporal resolution of 10 min, the kinetics of glucose consumption, lactate production and 13C incorporation into glutamate, alanine and glycogen. In control immature rat uteri, under aerobic conditions, the rates (+/- SEM) of [1-13C]glucose consumption and [3-13C]lactate production were 24 +/- 2 and 7.5 +/- 0.5 mmol/g wet weight/h. The rates of synthesis of [4-13C]glutamate, [3-13C]alanine and 13C labeling of glycogen at C1 of its glucose moieties were significantly lower and were in the range 0.3-0.6 mmol/g wet weight/h. Thus, ca 35% of the labeled glucose was accounted for by the glycolytic and other observed pathways. In vitro stimulation of the uteri by estrogen was found to increase significantly, within 1 h, glucose consumption by 80%, lactate production by 150% and glutamate and glycogen synthesis by 150%, in parallel to a rapid hormonal induction of mRNA for the brain type isozyme of creatine kinase.

Characterization of ovarian follicular fluids of sheep, pigs and cows using proton nuclear magnetic resonance spectroscopy

Proton NMR spectra were produced for Graafian follicular fluids obtained by aspiration from sheep, pig and cow ovaries. The following low molecular mass, non-protein-bound metabolites were detected at concentrations exceeding 0.1 mM: acetate, alanine, creatinine/creatine, glycine, D-3-hydroxybutyrate, lactate, valine. Glucose was difficult to quantify and N-acetyl sugars gave a broad resonance at 2.06 ppm, presumably representing side-chains of glycoproteins. Ethanol was detected at up to millimolar concentrations in some specimens, though the physiological significance of this finding was not clear. The concentrations of all metabolites were comparable to those of plasma. These results have therefore shown that NMR spectroscopy is useful for gaining a broad and semiquantitative impression of the more abundant metabolites in the fluids of preovulatory Graafian follicles.

Smooth muscle intracellular pH: measurement, regulation, and function

Smooth muscle performs many functions that are essential for the normal working of the human body. Changes in pH are thought to affect many aspects of smooth muscle. Despite this, until recently little was known about either intracellular pH (pHi) values or pHi regulation in smooth muscle. Recent work measuring pHi with either microelectrodes or nuclear magnetic resonance spectroscopy is now providing some of this much needed information for smooth muscles. From these studies, it can be concluded tentatively that pHi is the same in different smooth muscles, approximately 7.06 (37 degrees C). This value is very close to those obtained in cardiac and skeletal muscle. It is clear that H+ is not in equilibrium across the smooth muscle membrane; i.e., pHi is regulated. Preliminary results in smooth muscle suggest that certain aspects of this regulation are different from that described for other muscle types. Changes in pHi have been found to produce marked effects on contraction in smooth muscle. Of particular interest is the fact that, unlike striated muscles, some smooth muscles can product more force during an intracellular acidification.