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Stretch-Induced Increases in Intracellular Ca Stimulate Thick Ascending Limb O2- Production and Are Enhanced in Dahl Salt-Sensitive Rats.


ABSTRACT: Mechanical stretch raises intracellular Ca (Cai) in many cell types. Luminal flow-derived stretch stimulates O2- production by thick ascending limbs (THALs). Renal O2- is greater in Dahl salt-sensitive (SS) than salt-resistant (SR) rats. We hypothesized that mechanical stretch stimulates Ca influx via TRPV4 (transient receptor potential vanilloid type 4) which in turn raises Cai in THALs; these increases in Cai are necessary for stretch to augment O2- production; and stretch-stimulated, and therefore flow-induced, O2- production is enhanced in SS compared with SR THALs due to elevated Ca influx and increased Cai. Cai and O2- were measured in SS and SR THALs from rats on normal salt using Fura2-acetoxymethyl ester and dihydroethidium, respectively. Stretch raised Cai in SS by 270.4±48.9 nmol/L and by 123.6±27.0 nmol/L in SR THALs (P<0.02). Removing extracellular Ca eliminated the increases and differences in Cai between strains. Knocking down TRPV4 in SS THALs reduced stretch-induced Cai to SR levels (SS: 92.0±15.9 nmol/L; SR: 123.6±27.0 nmol/L). RN1734, a TRPV4 inhibitor, blunted stretch-elevated Cai by ?75% and ?66% in SS (P<0.03) and SR (P<0.04), respectively. Stretch augmented O2- production by 58.6±10.2 arbitrary fluorescent units/min in SS and by 24.4±2.6 arbitrary fluorescent units/min in SR THALs (P<0.05). Removal of extracellular Ca blunted stretch-induced increases in O2- and eliminated differences between strains. RN1734 reduced stretch-induced O2- by ?70% in SS (P<0.005) and ?60% in SR (P<0.01). Conclusions are as follows: (1) stretch activates TRPV4, which raises Cai in THALs; (2) the increase in Cai stimulates O2- production; and (3) stretch-induced O2- production is enhanced in SS THALs due to greater increases in Cai.

SUBMITTER: Saez F 

PROVIDER: S-EPMC7058965 | biostudies-literature | 2020 Feb

REPOSITORIES: biostudies-literature

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Stretch-Induced Increases in Intracellular Ca Stimulate Thick Ascending Limb O<sub>2</sub><sup>-</sup> Production and Are Enhanced in Dahl Salt-Sensitive Rats.

Saez Fara F   Hong Nancy J NJ   Cabral Pablo D PD   Garvin Jeffrey L JL  

Hypertension (Dallas, Tex. : 1979) 20191223 2


Mechanical stretch raises intracellular Ca (Ca<sub>i</sub>) in many cell types. Luminal flow-derived stretch stimulates O<sub>2</sub><sup>-</sup> production by thick ascending limbs (THALs). Renal O<sub>2</sub><sup>-</sup> is greater in Dahl salt-sensitive (SS) than salt-resistant (SR) rats. We hypothesized that mechanical stretch stimulates Ca influx via TRPV4 (transient receptor potential vanilloid type 4) which in turn raises Ca<sub>i</sub> in THALs; these increases in Ca<sub>i</sub> are nece  ...[more]

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