Table 1.

Representative Osmolyte Concentrations (mOsM)^a–d

	interstitial	intracellular
Na +	135.0	15.0
K +	5.0	150.0
H 3 o +	0.00005	0.0001
Ca 2+	1.5	0.0001 [free]; 0.01 [total]
Mg 2+	0,5	0.5 [free]; 10 [total]
other cations	1.5	3.5
Cl −	105.0	15.0
HC0 3 −	30.0	10.0
small molecule metabolite anions	3.0	135.0a,b
protein anions	7.5a	9.5a,c,d
small molecule metabolites		40.0a,b
RNA		0.5d
lipids		0.05d
DIMA		0.000005d
total osmolytes	289	379
H 2 0 mole fraction (OsX w )	0.995	0.993
H 2 0 millimolarity (mM)	45,000e	42,000f
f w	fw,o = 45/55 = 0.82	fw,i = 42/55 = 0.76
osmotic stoichiometry (H 2 O/osmolyte)	45/0.289 = ~156	42/0.379 = ~111

References (47–62).

^aref. (48),

^bref. (47),

^cref. (49),

^dref. (50),

^eref. (62),

^fref. (51).