ET-1 affects biology of hyaluronic acid (HA) in rat PASMCs. (A) HA in PASMC supernatant increases in response to ET-1, and was inhibited by ETA antagonism but not by ETB antagonism. (B) Hyaluronan synthase (HAS)–2 transcripts slightly increase in response to ET-1, and this increase was independent of ETA or ETB. hyaluronidase (HYAL)–2 decreases in response to ET-1, and was reversed by the antagonism of ETA, but not of ETB. (C) Incubation for 24 hours of rat PASMCs with ET-1 induces prolonged HA-mediated THP-1 monocyte adhesion lasting 3 days. The treatment of PASMCs with ATF6 shRNA or salubrinal did not abrogate HA-mediated THP-1 adhesion. (D, from top left to right) PKH26-labeled THP-1 cells (arrows) do not adhere to untreated PASMCs, and HA is barely detectable. When PASMCs are treated with either tunicamycin or ET-1 for 24 hours, THP-1 cells adhere and HA can be detected, except if treated with hyaluronidase (HAse) before THP-1 cell incubation (bottom left). THP-1 cells persistently adhered, and HA remained detectable, at 48 and 72 hours after the stimulation by ET-1 of PASMCs (lower middle and right). *P < 0.05, compared with DMSO. **P < 0.05, compared with ET-1 alone. Bar = 10 μm.