Difficulties in detecting parathyroid hypertensive factor in the rat

1. Parathyroid hypertensive factor (PHF) has been implicated in the pathogenesis of several forms of hypertension. We aimed to establish a PHF bioassay using spontaneously hypertensive rat (SHR) plasma. 2. Spontaneously hypertensive rats were confirmed hypertensive and their plasma was dialysed and injected into anaesthetized normotensive rats. 3. Haemodynamic responses to injected SHR plasma were uninterpretable during pentobarbital anaesthesia due to blood pressure (BP) fluctuation. Under halothane anaesthesia, BP was stable but did not rise following SHR plasma injection. Using filtered, undialysed plasma and a different brand of pentobarbital, no consistent BP response was observed following SHR plasma injection. 4. We were unable to detect PHF in the SHR.