Renal Interstitial Injection of a‐Trinositol Increases Renal Interstitial Hydrostatic Pressure (RIHP) but Does Not Modify its Low Frequency Oscillatory Pattern

Abstract

RIHP increases after renal interstitial medullary injection (RIMI) of a 5μ bolus of saline solution (SS) + 2 μM α‐Trinositol (α –T, drug that increases collagen fiber network contraction, FASEB J 31:701.4: 2017). To assess whether this increase is induced by changes in the frequency and/or amplitude of oscillatory pattern of RIHP we evaluate in hydropenic rats the time course of RIHP before and after either an acute sham (CTR group, n = 9) or an acute (1s) real RIMI of a 5μ bolus of either vehicle (0.9% SS, SS group, n = 9) or SS + 2 μM α ‐ T (α – T group, n = 9). Left subcapsular RIHP (RIHP) was continuously measured (1 Hz) in anesthetized rats with right nephrectomy, acute left renal denervation, hormonal clamp and renal perfusion pressure control (100 mmHg), before (baseline phase = BL = 30 min) and 30 min after (experimental phase = EXP) sham or real RIMI of 5 μl bolus of either SS or SS + α‐T. The table shows the 30 min average BL RIHP (1800 s, s = samples or seconds), ΔRIHP (EXP RIHP – BL RIHP) values (mean ± SEM) obtained 30 min after sham or real RIMI during 300 s. It also shows the RIHP frequency (F) of major oscillations (cycles/min = cpm) and the standard deviation (SD, an oscillatory amplitude index) of global RIHP oscillation before and 30 min after RIMI. Three were no differences among groups in BL RIHP, F or SD. For ΔRIHP data there were time * group interaction effect (P < 0.009); * P = 0.05, ** P < 0.001 vs. BL; • P < 0.04 vs. SS group, ¨P < 0.001 vs. CTR group. For SD data ° P <0.001 between phases. CONCLUSIONS The results show that RIHP oscillates at an equally low frequency (≈ 0.03 Hz) before and after sham or real RIMI but with lower amplitude after sham or real RIMI in any of the groups. This suggests that α‐T increases RIHP but not through modify the frequency or amplitude of its low frequency oscillatory pattern. Support or Funding Information Own financial resources of Integrative Physiology Lab. RIHP RIHP RIHP (mmHg) Frequency SD Delta cpm (mmHg) BL EXP‐BL BL EXP BL EXP 30 min at min 30 last 5 min at min 30 30 min at min 30 Group 1800 s 300 s 300 s 300 s 1800 s 300 s CTR 3.0 ± 0.10 −1.1 ± 0.16 2.2 ± 0.26** 2.1 ± 0.26 0.54 ± 0.07 0.20 ± 0.04° SS 3.1 ± 0.03 −0.15 ± 0.36 2.1 ± 0.44 2.2 ± 0.46 0.50 ± 0.06 0.18 ± 0.03° a‐T 3.1 ± 0.06 1.26 ± 0.51 2.2 ± 0.32*•♦ 2.2 ± 0.25 0.35 ± 0.04 0.19 ± 0.04°