Serum from young, sedentary adults who underwent passive heat therapy improves endothelial cell angiogenesis via improved nitric oxide bioavailability.

: Passive heat therapy improves vascular endothelial function, likely via enhanced nitric oxide (NO) bioavailability, although the mechanistic stimuli driving these changes are unknown. : To determine the isolated effects of circulating (serum) factors on endothelial cell function, particularly angiogenesis, and NO bioavailability. : Cultured human umbilical vein endothelial cells (HUVECs) were exposed to serum collected from 20 healthy young (22 ± 1 years) adults before (0 wk), after one session of water immersion (Acute HT), and after 8 wk of either heat therapy (N = 10; 36 sessions of hot water immersion; session 1 peak rectal temperature: 39.