Comparison of the digitalis receptor in erythrocytes from preterm infants and adults.
We compared 86rubidium by erythrocytes of preterm infants and adults as a measurement of their Na+, K+, ATPase enzyme system. In neonates, total uptake (0.92 +/- 0.13 micrograms/10(6) cells) and specific uptake (0.64 +/- 0.076 micrograms/10(6) cells) were significantly higher than in adults (0.52 +/- 0.1 and 0.29 +/- 0.06 micrograms/10(6) cells, respectively; p less than 0.025). The percentage of specific uptake from total uptake was higher in infants (73.3 +/- 2.3%) than in adults (57.9 +/- 4.6%) (p less than 0.005). No differences were found in the affinity constant of 86Rb uptake between infants (4.35 +/- 0.48 ng/ml) and adults (4.85 +/- 0.48 ng/ml). Stratification of infants according to their serum K+ concentrations revealed that levels above 5.4 mEq/liter were associated with a higher specific uptake (0.79 +/- 0.107 micrograms/10(6) cells) than in normokalemic infants (0.54 +/- 0.09 micrograms/10(6) cells) or adults (0.304 +/- 0.061 micrograms/10(6) cells) (p less than 0.05). The difference between hyperkalemic and normokalemic infants persisted after excluding those who received adult packed cells (0.88 +/- 0.1 and 0.6 +/- 0.12 micrograms/10(6) cells, respectively) (p less than 0.05). Infants with serum K+ greater than 5.8 mEq/liter received on average significantly more K+ in previous days (2.46 +/- 0.49 versus 1.13 + 0.34 mEq/kg.day; p less than 0.025). The different K+ level could not be attributed to different creatinine clearance in the two groups.
Koren
G
G
Division of Clinical Pharmacology, Hospital for Sick Children, Toronto, Ontario, Canada.
Long
D
D
Klein
J
J
Beatie
D
D
Bologa-Campeanu
M
M
Livne
A
A
Kirpalani
H
H
D000328:Adult; D004070:Digitalis / Q000378:metabolism*; D004912:Erythrocytes / Q000201:enzymology / Q000648:ultrastructure*; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature / Q000502:physiology*; D010946:Plants, Medicinal; D010947:Plants, Toxic; D011188:Potassium / Q000097:blood / Q000652:urine; D011955:Receptors, Drug / Q000378:metabolism*; D012413:Rubidium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D011955:Receptors, Drug; C027082:digitalis receptor; D000254:Sodium-Potassium-Exchanging ATPase; D012413:Rubidium; D011188:Potassium