Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, PCA147

Poster Communications

Calcium-dependent contraction of renal tubules

S. L. Svendsen1, A. Hofherr2, M. Köttgen2, J. Leipziger1

1. Biomedicine, Aarhus University, Aarhus, Denmark. 2. ZKF, University Hospital Freiburg, Freiburg, Germany.

Over several years, we have observed, that perfused renal tubules show "odd movements" when exposed to extracellular ATP. Whether this observation was merely an artefact or a relevant biological observation remained elusive. It is well known that renal tubules express a contractile machinery localized closely to the apical membrane. The functionality of this structure is enigmatic. Plate grown kidney cells show a pattern on their apical membrane consistent with active contraction of the luminal membrane domain. Here we test if isolated perfused renal tubules can contract. We measured the effect on tubular diameter in isolated murine thick ascending limbs (TAL), when inducing a cytosolic [Ca2+] ([Ca2+]i) increase with uncaging ATP/stimulation of the apical P2Y2 receptors. Uncaging luminal ATP elicited a marked increase of [Ca2+]i, which could be fully blocked by intracellular Ca2+ chelation following BAPTA-AM loading. Remarkably, within 40 seconds following apical P2Y2 receptor stimulation, both the inner and outer diameter of the perfused TAL were significantly reduced. The inner and outer diameter decreased by 0.236µm (SEM ±0.041, n=5) and 0.170 µm (SEM ±0.022, n=5), respectively. This reduction could be largely prevented either blocking the [Ca2+]i increase with BAPTA or by hindering actin-myosin interaction with highly specific antagonists. We report the remarkable observation that renal tubules in a [Ca2+]i -dependent manner can contract. This suggests that the diameter of renal tubules is a subject to active and acute regulation.

Where applicable, experiments conform with Society ethical requirements