Abstract: Objective To investigate insulin resistance and the effects of intravenous acute saline load on renal production of prostaglandin I2 (PGI₂) and thromboxane A₂ (TXA₂) in salt-sensitive hypertensive patients. Methods The 24-hour excretion of urinary 6-keto-prostaglandin F (PGF) 1α and thromboxane B₂ were measured before and after intravenous acute saline load in 53 hypertensive patients whose salt sensitivity had been determined. Oral glucose tolerance test and insulin release test were performed in all the subjects. Results after intravenous acute saline load, the 24-hour excretions of urinary 6-keto PGF 1α were significantly lower in salt-sensitive (SS) hypertensive patients than that in non-salt-sensitive (NSS) ones (316±57 pg/min vs 371±68 pg/min, P<0.01), and the decrease from baseline was much greater in SS group than that in NSS group (197±99 pg/min vs 136±101 pg/min, P<0.01). Both 24 hour urinary excretion of TXA₂ and the increase in urinary excretion of TXA₂ were significantly greater in SS hypertensive patients than those in NSS ones after salt loading (394±32 pg/min vs 359±44 pg/min, P<0.01, and 80±47 pg/min vs 47±45 pg/min, P<0.01, respectively). The plasma glucose and insulin concentrations in every time point were much higher in SS hypertensive subjects than that in NSS ones, and the former group had lower insulin sensitivity index than the latter (0.013±0.003 vs 0.018±0.004, P<0.01). Conclusion Saline load produces significantly different effects on renal production of PGI₂ and TXA₂ in SS and NSS hypertensive patients, and these changes may be related to the pathophysiology of SS hypertensive patients after acute salt loading. Insulin resistance is greater in SS hypertensive patients than in NSS ones.