Advances in experimental medicine and biology · 2026
The Role of Nitric Oxide in Regulating Microvascular Oxygen Pressure During Diaphragm Contraction in Rats.
СтатьяНазвание и аннотация: Перевод в очереди
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Hotta Kazuki, Fukuzaki Narumi, Kataoka Rin, Izawa Kota, Arai Shuri, Kamiya Kentaro, Matsunaga Atsuhiko
Аннотация
BACKGROUND: The diaphragm muscle is the primary muscle involved in inspiration and is unique to mammals. Because the diaphragm is a constantly active muscle, its contraction may depend on oxidative phosphorylation and O2 supply to create adenosine triphosphate. This study aimed to evaluate the role of intrinsic vasodilator nitric oxide (NO) in diaphragm O2 dynamics.
METHODS: Wistar male rats (n = 6, 10 wks old, 311 ± 14 g) were mechanically ventilated under isoflurane anesthesia. The diaphragm was exposed to measure microvascular partial O2 pressure (PO2mv) by phosphorescence quenching technique during electrical stimulation-induced diaphragm contractions (6 V, 2 ms, 2 Hz, 180 s). The 180 s of muscle contractions and PO2mv measurement were repeated 10 min after endothelial NO synthase inhibition by the intra-arterial infusion of nitro-l-arginine methyl ester (L-NAME; eNOS inhibitor). The PO2mv change during the transition from rest to contraction was fitted to a nonlinear regression model. Time delay, time constant (tau), rate constant (K), and nadir in PO2mv were calculated and compared before and after eNOS inhibition. [Results] Diaphragm PO2mv decreased during contractions both before and after eNOS inhibition. The time delay and K were not different before and after L-NAME. However, the L-NAME administration decreased the tau and nadir in PO2mv (tau, 7.61 [5.18-13.41] vs. 3.36 [1.81-5.57] s; nadir, 7.45 [1.41-14.85] vs. 3.93 [0.89-9.47] mmHg; before vs. after eNOS inhibition, median [25-75 percentiles], P < 0.05, respectively).
DISCUSSION: The time constant in PO2mv is determined by oxygen supply to the capillaries and oxygen utilization. The faster time constant and lower nadir in PO2mv possibly indicate the slower and lower oxygen supply to diaphragm capillaries after eNOS inhibition.
CONCLUSION: The NO has a crucial role in the diaphragm oxygen dynamics of intact rats.
METHODS: Wistar male rats (n = 6, 10 wks old, 311 ± 14 g) were mechanically ventilated under isoflurane anesthesia. The diaphragm was exposed to measure microvascular partial O2 pressure (PO2mv) by phosphorescence quenching technique during electrical stimulation-induced diaphragm contractions (6 V, 2 ms, 2 Hz, 180 s). The 180 s of muscle contractions and PO2mv measurement were repeated 10 min after endothelial NO synthase inhibition by the intra-arterial infusion of nitro-l-arginine methyl ester (L-NAME; eNOS inhibitor). The PO2mv change during the transition from rest to contraction was fitted to a nonlinear regression model. Time delay, time constant (tau), rate constant (K), and nadir in PO2mv were calculated and compared before and after eNOS inhibition. [Results] Diaphragm PO2mv decreased during contractions both before and after eNOS inhibition. The time delay and K were not different before and after L-NAME. However, the L-NAME administration decreased the tau and nadir in PO2mv (tau, 7.61 [5.18-13.41] vs. 3.36 [1.81-5.57] s; nadir, 7.45 [1.41-14.85] vs. 3.93 [0.89-9.47] mmHg; before vs. after eNOS inhibition, median [25-75 percentiles], P < 0.05, respectively).
DISCUSSION: The time constant in PO2mv is determined by oxygen supply to the capillaries and oxygen utilization. The faster time constant and lower nadir in PO2mv possibly indicate the slower and lower oxygen supply to diaphragm capillaries after eNOS inhibition.
CONCLUSION: The NO has a crucial role in the diaphragm oxygen dynamics of intact rats.