Decreased L-type calcium current in antral smooth muscle cells of STZ-induced diabetic rats.

Abstract

BACKGROUND:

Diabetic gastroparesis (delayed gastric emptying) is associated with antral hypomotility. L-type Ca(2+) channels play an important role in generation of action potentials and activation of contractions. This study was designed to investigate if the function of the L-type Ca(2+) channels of antral circular smooth muscle cells (SMCs) is impaired in streptozotocin (STZ)-induced diabetic rats.

METHODS:

Eight weeks after the injection of STZ or vehicle, whole-cell patch clamp was used to record Ca(2+) currents, and isometric tension recording was used to measure Ca(2+) influx-induced contractions in circular muscle strips. Solid gastric emptying was measured in diabetic and control rats. Protein expression of Ca(2+) αlC-subunit in antral smooth muscles was compared between diabetic and control rats.

KEY RESULTS:

(1) Solid gastric emptying, independent of age or bodyweight, was slower in the diabetic rats, even after acute correction of hyperglycemia. (2) Verapamil, a potent calcium channel blocker, dose dependently reduced solid gastric emptying in normal rats. (3) Current density of L-type Ca(2+) channel at 10 mV in antral circular SMCs was significantly decreased in the diabetic rats (-9.8 ± 0.7 pA/pF vs -15.9 ± 1.0 pA/pF in control, p < 0.001). However, protein expression of the Ca(2+) channel in antral muscles did not differ between diabetic and control rats. (4) Contractile responses to 1 and 3 mM [Ca(2+) ] were significantly reduced in the diabetic antral circular muscle strips, indicative of reduced Ca(2+) influx.

CONCLUSIONS & INFERENCES:

These data suggested that the decreased L-type Ca(2+) current in antral SMCs may contribute to antral hypomotility in STZ-induced diabetic rats.

• Authors: S Li, J D Z Chen
• Journal: Neurogastroenterology and motility : the official journal of the European Gastrointestinal Motility Society (Neurogastroenterol Motil) Vol. 26 Issue 7 Pg. 971-9 (Jul 2014) ISSN: 1365-2982 [Electronic] England
• PMID: 24758401 (Publication Type: Journal Article)
• Copyright: © 2014 John Wiley & Sons Ltd.

Chemical References

• Calcium Channel Blockers
• Calcium Channels, L-Type
• Verapamil
• Calcium

Topics

• Action Potentials (drug effects, physiology)
• Animals
• Calcium (metabolism)
• Calcium Channel Blockers (pharmacology)
• Calcium Channels, L-Type (metabolism, physiology)
• Diabetes Mellitus, Experimental (metabolism, physiopathology)
• Gastric Emptying (drug effects, physiology)
• Muscle Contraction (drug effects, physiology)
• Myocytes, Smooth Muscle (metabolism, physiology)
• Rats
• Rats, Sprague-Dawley
• Verapamil (pharmacology)