Kolanut (Kola nitida) Enhances Antidiuretic Activity in Young Dehydrated Subjects

We have studied the influence of kolanut (approximately 0.50 g/kg body weight) on thirst and fluid intake, as well as urine output in young and elderly control and dehydrated healthy subjects in the North and South-West of Nigeria. Fluid intake was either ad libitum (water only) or a fixed load of approximately 17.5 mL/kg of either water or 0.9% NaCl orally. Thirst rating and urine output were determined every 30 min for up to 120 min. The 12 h urine output in the northern part of the country was lower than that in the southern part. Dehydration reduced the 12 h urine output and increased thirst rating in both young and elderly subjects. Much of the drinking associated with thirst took place within the first 30 min of provision of water. There is a significant relationship between thirst rating and the amount of fluid intake during this period. Kolanut stimulates drinking and elevates thirst rating. However, when urine output was expressed as a percentage of the fluid intake/load, kolanut significantly reduced the excretion of water in only the dehydrated subjects suggesting that kolanut may be potentiating antidiuretic hormone activity in circulation. This was significant only in the young subjects. Since this response was blunted in normal saline loaded subjects, the results further suggest that a change in plasma osmolality (rather than volume) is the major determinant of plasma antidiuretic activity affected by kolanut. It can be concluded that kolanut enhances plasma antidiuretic activity and this is related to a change in plasma osmolality and to the age of subjects.