Gontijo J A, Silva-Netto C R, Furtado M R
Departamento de Clínica Médica, Faculdade de Ciências Médicas, Universidade Estadual de Campinas, SP, Brasil.
Braz J Med Biol Res. 1990;23(11):1205-8.
Studies were undertaken to characterize the participation of specific alpha-1,alpha-2 and beta adrenoceptors of the lateral hypothalamic area (LHA) in the urinary excretion of sodium and potassium. Alpha-1 and alpha-2 LHA receptors were shown to participate in the regulation of renal sodium and potassium excretion. The effects of noradrenaline microinjection (30 nmol in 1 microliter) into the LHA on urinary sodium excretion (UNaV) are blocked by previous injection of the alpha-1 antagonist prazosin (4 nmol in 1 microliter) from 3.22 +/- 0.25 to 0.59 +/- 0.04 microEq min-1 100 g body weight-1. Pre-injection of yohimbine, an alpha-2 antagonist (4 nmol in 1 microliter), synergistically potentiated the action of noradrenaline on UNaV (3.22 +/- 0.25 to 4.02 +/- 0.27 microEq min-1 100 g body weight-1) and on urinary potassium excretion (UKV) (0.70 +/- 0.08 to 1.15 +/- 0.12 microEq min-1 100 g body weight-1). The beta-adrenergic blockers metoprolol (100 nmol in 1 microliter) and propranolol (100 nmol in 1 microliter) had no synergistic or antagonistic action on the sodium excretion fraction, suggesting that neither of these receptors is present in LHA. Our results indicate that natriuresis occurs even in the absence of changes in glomerular filtration rate and demonstrate an inhibitory natriuretic effect of an alpha-1 blocker (prazosin) injected into the LHA before adrenaline, while an alpha-2 antagonist (yohimbine) yielded a potentiating effect.
开展了多项研究以明确下丘脑外侧区（LHA）特定的α-1、α-2和β肾上腺素能受体在钠和钾尿排泄中的作用。研究表明，α-1和α-2 LHA受体参与肾钠和钾排泄的调节。预先注射α-1拮抗剂哌唑嗪（1微升含4纳摩尔）可使LHA内微量注射去甲肾上腺素（1微升含30纳摩尔）对尿钠排泄（UNaV）的影响受到阻断，从3.22±0.25微当量·分钟⁻¹·100克体重⁻¹降至0.59±0.04微当量·分钟⁻¹·100克体重⁻¹。预先注射α-2拮抗剂育亨宾（1微升含4纳摩尔）可协同增强去甲肾上腺素对UNaV（从3.22±0.25微当量·分钟⁻¹·100克体重⁻¹增至4.02±0.27微当量·分钟⁻¹·100克体重⁻¹）以及对尿钾排泄（UKV）（从0.70±0.08微当量·分钟⁻¹·100克体重⁻¹增至1.15±0.12微当量·分钟⁻¹·100克体重⁻¹）的作用。β肾上腺素能阻滞剂美托洛尔（1微升含100纳摩尔）和普萘洛尔（1微升含100纳摩尔）对钠排泄分数无协同或拮抗作用，提示LHA中不存在这两种受体。我们的结果表明，即使肾小球滤过率无变化也会发生利钠作用，并证明在肾上腺素之前向LHA注射α-1阻滞剂（哌唑嗪）具有抑制利钠作用，而α-2拮抗剂（育亨宾）则产生增强作用。
