In vivo and in vitro effects of lead on vascular reactivity in rats.

The effects of lead on vascular responsiveness were examined in rats. Adult rats, which had received levels of lead acetate in their drinking water to produce blood levels similar to those seen in some urban human populations, consistently had higher systolic blood pressures compared to age-matched controls. Helical strips of tail arteries from the lead-treated rats displayed a greater force-generating ability in response to the cumulative addition of methoxamine to the muscle bath. There were no differences in ED50 between the two groups. Similar results were obtained when norepinephrine was used. The calcium-entry blocker, D 600, was less effective in reducing in reducing contractions induced by methoxamine in lead-treated rats than in controls. There were no differences between the two groups in responses to KCl or electrical stimulation of nerve endings. Contractile responses to norepinephrine, methoxamine, KCl, and nerve stimulation in arteries from untreated rats were unaltered by addition of lead acetate to the muscle bath. These results demonstrate that hypertension induced by moderate levels of lead intake is associated with an increased vascular responsiveness to alpha-adrenergic agonists.