Table 1.

Elemental concentrations in secretory vesicles of isolated rat neurohypophysical nerve endings

Condition and location		Conc., mmol/kg dry weight				Na/S regression R2 (probability)	Na/Cl regression R2(probability)
	n	Na	S	Cl	Ca
Control
Peripheral vesicles	64	60  ±  6	836  ±  22	50  ±  4	3.3  ±  0.8	0.0002 (P = 0.92)	0.38 (P = 0.0001)
Internal vesicles	94	38  ±  3	814  ±  20	50  ±  3	4.2  ±  0.9	0.0005 (P = 0.83)	0.21 (P = 0.0001)
Stimulated 6 min
Peripheral vesicles	84	99  ±  7**	750  ±  18*	57  ±  5	4.9  ±  0.7*	0.11 (P = 0.001)	0.05 (P = 0.04)
Internal vesicles	66	50  ±  4*	814  ±  19	46  ±  5	4.9  ±  1.1	0.008 (P = 0.47)	0.03 (P = 0.12)
Stimulated 20 min
Peripheral vesicles	67	71  ±  6*	775  ±  18*	74  ±  5**	5.6  ±  1.0*	0.004 (P = 0.61)	0.09 (P = 0.01)
Internal vesicles	101	33  ±  2	808  ±  18	62  ±  3**	6.9  ±  1.1*	0.006 (P = 0.44)	0.006 (P = 0.42)

Data are given as mean ± SEM. Column n is the number of vesicles analyzed; the number of endings analyzed ranged from 33 to 35 per experimental condition. Concentrations in mmol/kg dry weight can be converted to mmol/kg wet tissue by dividing by a factor of 2 (see Materials and Methods). Concentrations were also obtained for several other elements as follows (range in parentheses): Mg (36–45); P (126–149); K (98–137). The correlation, when significant, is negative for Na/S and positive for Na/Cl. The R² probability was obtained by ANOVA. Significantly different from control values by Mann–Whitney test: ∗, P < 0.05; ∗∗, P < 0.001.