Influence of model melanoidins on calcium-dependent transport mechanisms in smooth muscle tissue.
Melanoidins obtained from L-arginine and D-glucose (MW > 3500 Da) were tested for their ability to influence the contractility of gastric smooth muscles. A study within the range 0.1-10 mg/mL revealed that at low concentrations, the melanoidins provoked concentration-dependent contraction, whereas a muscle relaxation was registered at high concentrations. The contraction was preceded by changes in the calcium membrane current as measured by single sucrose-gap method and significantly attenuated by the calcium channel blockers D-600 and nifedipine. Measurements with Ca(2+)-selective electrode showed that the melanoidins decreased the concentration of ionized Ca(2+ )in tissue bath in concentration-dependent manner. Experiments carried out in solutions with lower than normal Ca(2+) concentration and using melanoidins preliminary saturated with Ca(2+ )confirmed that the calcium chelation by melanoidins was a key contributing cause for the development of relaxant response. The results obtained showed that the melanoidins could influence the contractility of smooth muscles through at least two pathways: at low concentrations they caused depolarization and activation of L-type calcium channels, stimulated the Ca(2+ )influx, and provoked contraction, whereas at high concentrations calcium binding by melanoidins led to significant depletion of extracellular calcium ions and contributed to the relaxation process observed.
Stefanova
Iliyana D
ID
Department of Biophysics, Medical University, Plovdiv, Bulgaria.
Argirova
Mariana D
MD
Krustev
Athanas D
AD
D000818:Animals; D001120:Arginine / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000032:analysis / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D004553:Electric Conductivity; D005711:Gallopamil / Q000494:pharmacology; D005947:Glucose / Q000494:pharmacology; D007552:Isotonic Solutions; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects* / Q000378:metabolism*; D009543:Nifedipine / Q000494:pharmacology; D011108:Polymers / Q000494:pharmacology*; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013270:Stomach
D002121:Calcium Channel Blockers; D007552:Isotonic Solutions; C051865:Krebs-Ringer solution; D011108:Polymers; C011908:melanoidin polymers; D005711:Gallopamil; D011189:Potassium Chloride; D001120:Arginine; D009543:Nifedipine; D005947:Glucose; D002118:Calcium