906 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS markable difference between hair follicle and muscle metabolism is in the pentose cycle activity, which is insignificant in muscle. The metabolic characteristics of growing and resting hair follicles differ remarkably. Growing hair follicles utilize glucose twice as fast as those resting. Although lactate is the major product in both types of hair follicles (specific yield being 90 to 99(•o), the rate of lactate pro- duction in the growing follicle is double that in the resting. The calculated contribution of the pentose cycle to glucose utilization in the growing follicle is four times that in the resting (Table II). A bal- ance sheet of glucose carbon utilization further illustrates the differ- ence between growing and resting hair follicles and shows that the pentose cycle activity in the growing follicles is about 400% greater than that in the resting follicle (Table III). The contribution of both the TCA cycle and the pathway to fatty acid synthesis also appears to be increased. Table IV compares energy production in the growing and resting hair follicles. In both types, one mole of glucose yields a net of about 3 moles of ATP, roughly two-thirds from cytoplasmic me- tabolism and one-third via the respiratory chains. Energy production in hair follicles is not very efficient, most of the glucose being converted to lactate. However, the activity of the TCA cycle increases about 35% during the growth stage of the hair follicle. The pyridine nucleotide balance is shown in Table V. The increase in reduced triphosphopyri- dine nucleotide (TPNH) formation in the growing follicle is marked. In Tables III and IV, the ATP and carbon balance charts are based on the utilization of 100 vmoles of glucose. However, the actual values Table III The Carbon Balance Growing Resting Products (t• atom carbon/100 t•moles glucose utilized) -- CO2 from Pentose cycle 7.5 1.8 Py. decarboxy. 7.5 5.5 TCA cycle 13.0 9.5 Lact ate 5 69 5 81 Fatty acids 1.8 1.3 Glycerol 0.6 0.5 Glycogen 2.5 1.2 DNA protein 2.5 2.6

HUMAN HAIR FOLLICLES 907 Table IV The ATP Balance Growing Resting (t•moles/100 t•moles glucose utilized) Utilization Hexokinase 100 100 P-fructokinase 97.5 99.8 Ac. CoA carboxy. 1.0 1.0 Ac. CoA transfer Sum ca. 200 ca. 200 Formation G-3-P DH 197 201.5 Pyruvate kinase 197 199.6 Pyr. DH (P/O = 3) 23 19 TCA cycle 78 57 Sum ca. 500 ca. 480 Net -3-300 -3-280 Table V Pyridine Nucleotide Balance (Cytoplasmic) Hair Follicles Growing Resting (t•moles/100 t•moles glucose utilized) TPNH DPNH TPNH DPNH Formation Pentose cycle 15.0 ... 3.6 ... G3P DH ... 197 ... 200 Utilization Fatty acid synthesis 1.6 ... 1.1 ... Glycerol ... 0.2 ... 0.2 Lactate ... 190 ... 193 Net 13.4 6.8 2.5 6.8 for growing follicles are twice those for resting, because the growing ones utilize glucose about twice as fast as the resting. The net shifts in the metabolic pathways during the transformation of the resting into the growing stage of hair follicles can be summarized as follows: compared with that in resting follicles, glucose utilization in growing follicles in- creases 200%, glycolysis 200%, activity of the penrose cycle 800%, metabolism by other pathways 150%, and ATP production via the res- piratory chains 270%. Thus, in the growing hair follicles, glucose