Mechanosensitive Proteins in Regulating Heart Rate in Larval Drosophila

Abstract

Background and Objective: Invertebrates to mammals attempt to maintain heart rate under different physiological and pathological conditions by directly stretching myocytes as well as hormonal and neural regulation. Contractility increases with stretching of a heart tube in insect larvae as well as for the large ventricles of a mammal. This is a result of stretch activated ion channels, one type being transient receptor protein-ankyrin (TrpA) receptors. These TrpA receptors are known to increase in expression in cardiac pathologies of mammals, but it is not known if this is beneficial or detrimental. Hence the objective of the current study was to increase expression of the mechanosensitive channels (TrpA1) in the larval Drosophila heart to determine if they were responsible for maintaining the heart rate during pulsatile perfusion. Materials and Methods: Drosophila lines were constructed so the F1 generation selectively expressed TrpA1 in cardiac tissue. Larvae were dissected to expose the hearts to pulsatile perfusion for 4 hrs. The heart rates were counted and compared for significance using an ANOVA or Wilcoxon rank sum test. Results: Pulsatile supra-perfusion helps to maintain heart beats for over four hrs in situ which allows prolonged physiological and pharmacological studies. The parental (UAS-TrpA1) and over expressors (Tinc>TrpA1) of receptors relatively maintained heart rate at 20 E C for about 4 hrs. At 30 E C the parental line (UAS-TrpA1) was able to maintain heart rate better than the over expressors (Tinc>TrpA1). Conclusion: The TrpA1 blocker, HC-030031 at 30 µM, 100 µM and 1 mM, did not block the induced depolarization of body wall muscle at 30 E C for larvae expressing TrpA1 receptors. Controls also did not show an effect with exposure to HC-030031