Roberts L A, Hughes M J
Am J Physiol. 1977 Aug;233(2):H228-33. doi: 10.1152/ajpheart.1977.233.2.H228.
Spontaneously beating rabbit atria responded to hyperosmotic Tyrode bathing media with an increase in rate, force of contraction, and passive tension dependent on the level of osmolality and the osmotic agent employed. The positive chronotropic response reached a maximum within a few minutes and then declined to a lower, maintained plateau level. The plateau change in rate was similar whether the osmotic agent added to Tyrode solution was sucrose, mannitol or NaCl. For these agents, the response increased linearly with osmotic pressure of the bathing media from 300 to 500 mosmol/kg H2O, then progressively decreased approaching zero (plateau rate = control) at about 700 mosmol/kg H2O. The chronotropic response to urea in Tyrode solution, though less than for the other three agents, progressively increased over the entire range of osmolalities tested (from 300 to 700 mosmol/kg H2O). The inotropic response was positive for all agents from 300 to 600 mosmol/kg H2O. Passive tension of atria increased with added NaCl, sucrose, or mannitol, but not with urea. Propranolol did not alter the atrial response to hyperosmolality. Thus, we find that the chronotropic response of atria to hyperosmolar solutions is positive over a wide range of agents and osmolalities, in contrast to earlier reports of a direct negative chronotropic effect.
自发性搏动的兔心房对高渗的台氏液灌流介质的反应是频率、收缩力和被动张力增加，这取决于渗透压的水平和所使用的渗透剂。正性变时反应在几分钟内达到最大值，然后下降到一个较低的、稳定的平台水平。无论添加到台氏液中的渗透剂是蔗糖、甘露醇还是氯化钠，频率的平台变化都是相似的。对于这些试剂，反应随着灌流介质的渗透压从300 mosmol/kg H₂O线性增加到500 mosmol/kg H₂O，然后在约700 mosmol/kg H₂O时逐渐下降至接近零（平台频率 = 对照）。台氏液中尿素的变时反应虽然小于其他三种试剂，但在测试的整个渗透压范围内（从300到700 mosmol/kg H₂O）逐渐增加。从300到600 mosmol/kg H₂O，所有试剂的变力反应都是正性的。心房的被动张力随着添加氯化钠、蔗糖或甘露醇而增加，但不随尿素增加。普萘洛尔不改变心房对高渗的反应。因此，我们发现与早期关于直接负性变时效应的报道相反，心房对高渗溶液的变时反应在广泛的试剂和渗透压范围内是正性的。
