Pharmacological inactivation of the primate posterior insular/secondary somatosensory cortices attenuates thermal hyperalgesia

BACKGROUND

We previously established a macaque model of central post-stroke pain (CPSP) and confirmed the involvement of increased activity of the posterior insular cortex (PIC) and secondary somatosensory cortex (SII) to somatosensory stimuli in mechanical allodynia by a combination of imaging techniques with local pharmacological inactivation. However, it is unclear whether the same intervention would be effective for thermal hyperalgesia. Therefore, using the macaque model, we examined behavioral responses to thermal stimuli following pharmacological inactivation of the PIC/SII.

METHODS

Two CPSP model macaques were established based on collagenase-induced unilateral hemorrhagic lesions in the ventral posterolateral nucleus of the thalamus. To evaluate pain perception, withdrawal latencies to thermal stimuli of 37, 45, 50, 52, and 55 °C to hands were measured. Several weeks after the lesion induction, pharmacological inactivation of the PIC/SII by microinjection of muscimol was performed. The effect of inactivation on withdrawal latency was assessed by comparison with withdrawal latency after vehicle injection.

RESULTS

Several weeks after induction of the thalamic lesions, both macaques demonstrated a reduction in withdrawal latencies to thermal stimulation (<50 °C) on the contralesional hand, indicating the occurrence of thermal hyperalgesia. When the PIC/SII were inactivated by muscimol, the withdrawal latencies to thermal stimuli of 50 and 52 °C were significantly increased compared to those after vehicle injection.

CONCLUSIONS

Our data emphasize that increased activity in the PIC/SII after appearance of thalamic lesions can contribute to abnormal pain of multiple modalities, and the modulation of PIC/SII activity may be a therapeutic approach for thermal hyperalgesia.

Oncoplastic breast surgery combining partial mastectomy with V-rotation mammoplasty for breast cancer on the upper inner area of the breast

The treatment of early breast cancer using breast conservation therapy (BCT) commonly ensures local control and acceptable cosmetic results. We herein report a useful technique for obtaining symmetry of the breast shape and a level inframammary line and nipple-areola that achieved excellent results. Four Japanese patients with early breast cancer located on the upper inner area of the breast were enrolled into this study. De-epithelialized skin close to the resected area and skin from the epigastric area with subdermal fatty tissue were moved to repair the defect. Oncoplastic breast surgery (OBS) combining partial mastectomy with the V-rotation mammoplasty technique was useful for patients with breast cancer on the upper inner area of minimal ptotic breasts.

Oncoplastic breast surgery combining partial mastectomy with a triangular skin resection and re-centralization of the nipple-areola

The treatment of early breast cancer using breast conservation therapy (BCT) commonly ensures local control and acceptable cosmetic results. We herein report a useful technique to obtain symmetry of the breast shape and a level inframammary line and nipple-areola, which achieved excellent results. Six Japanese patients with early breast cancer located on the upper area of the breast were enrolled into this study. A triangle-shaped area of skin was removed together with cancerous and healthy-surrounding breast tissue. Two crescents were designed and de-epithelialized in the directions of 9 o'clock and 3 o'clock. The width of the crescent was decided to be the same as a half or the length of the base of a triangle to be removed. After partial mastectomy, the inner and outer glandular flaps were horizontally sutured. The operations were simple to perform and were not associated with any postoperative complications. Oncoplastic breast surgery combining partial mastectomy with triangular skin resection and re-centralization of the nipple-areola was useful for patients with breast cancer on the upper quadrant area of non-ptotic breasts.

Expression of SOX9 Is Related to Prognosis in Patients with Oesophageal Squamous Cell Carcinoma

BACKGROUND

Sex-determining region Y-box 9 (SOX9) is an important transcription factor for the development and differentiation of cells and their organization. In the present study, the clinical significance of SOX9 expression in oesophageal squamous cell carcinoma was examined.

MATERIALS AND METHODS

SOX9 expression in surgical specimens of primary tumours were immunohistochemically investigated in 175 patients with oesophageal squamous cell carcinomas.

RESULTS

SOX9 was expressed (moderately or strongly) in 62.9% of samples. Expression of SOX9 was significantly positively correlated with depth of invasion, advanced stage, lymphatic and venous invasion, and poor prognosis. Univariate analysis showed that depth of invasion, lymph node metastasis, distant metastasis, stage, lymphatic invasion, venous invasion, and SOX9 expression were prognostic factors. Multivariate analysis indicated that depth of invasion and stage were independent prognostic factors, but SOX9 expression was not.

CONCLUSION

SOX9 expression is related to prognosis in patients with oesophageal squamous cell carcinoma, although it is not an independent prognostic factor.

Pancreaticogastrostomy after Pancreaticoduodenectomy Using Twin Square Wrapping with Duct-to-Mucosa Anastomosis

Background/Purpose: This study aimed to evaluate the feasibility and safety of a novel pancreaticogastrostomy technique for diminishing pancreatic fistulas after pancreaticoduodenectomy using gastric wrapping of the pancreatic stump with a twin square-shaped horizontal mattress and a suture fixing the main pancreatic duct to the gastric mucosa anastomosis [twin square wrapping (TSW) method]. Methods: Fifty-three patients undergoing pancreaticogastrostomy after pancreaticoduodenectomy were included in the study and chronologically divided into a conventional group (n = 32) and a TSW group (n = 21). The perioperative factors and the postoperative outcomes were retrospectively analyzed. Results: The operating time for the pancreatic anastomosis, the total operating time, and the blood loss volume in the TSW group were lower than in the conventional group, but without a statistically significant difference. The TSW group had a significantly lower postoperative white blood cell count and C-reactive protein level, with a reduced intra-abdominal fluid accumulation as assessed by computed tomography on postoperative day 7, had a lower incidence of postoperative complications and pancreatic fistulas, and achieved a shorter duration of drain placement and shorter postoperative hospital stays as compared to the conventional group. Conclusions: The TSW technique should be considered for reducing pancreatic fistulas by diminishing the postoperative inflammatory response and improving patient outcomes without increasing the operating time.

Chemical mapping of tulobuterol in transdermal tapes using microscopic laser Raman spectroscopy

Microscopic Laser Raman Spectroscopy and Mapping (MLRSM) technique was used to investigate the distribution of tulobuterol (TBR) crystals in transdermal tapes. TBR is one of suitable compounds for the transdermal pharmaceuticals because it has high permeability into skin. In case of TBR transdermal tapes, some commercial products also contain TBR crystals in order to control a release rate from a matrix. Therefore, the presence of TBR crystals in the matrix is a critical factor for quality assurance of this type of TDDS tapes. The model tapes prepared here employed two kinds of matrices, i.e., rubber or acrylic, which are generally used for transdermal pharmaceuticals. TBR crystals in the matrix were observed by MLRSM. Accurate observation of the distribution of TBR in the tapes was achieved by creating a Raman chemical map based on detecting unique TBR peak in each pixel. Moreover, differences in the growth of TBR crystals in the two kinds of matrices were detected by microscopic observation. MLRSM also enabled the detection of TBR crystals in commercial products. The present findings suggest that Raman micro-spectroscopic analysis would be very useful for verifying and/or assessing the quality of transdermal pharmaceuticals in development, as well as for manufacturing process control.

Developmental changes in the expression of growth-associated protein-43 mRNA in the monkey thalamus: northern blot and in situ hybridization studies

The expression of growth-associated protein-43 has been related to axonal elongation and synaptic sprouting. Using the Northern blot analysis, we investigated the developmental changes of growth-associated protein-43 mRNA in the thalamus of macaque monkeys. The amount of growth-associated protein-43 mRNA was high at embryonic day 125, and decreased at postnatal day 1. It increased again at postnatal day 8, reached its peak value at postnatal days 50-70, and then decreased gradually until postnatal year 1. We previously reported that the amount of growth-associated protein-43 mRNA in the cerebral cortex decreased roughly exponentially during perinatal and postnatal periods and that it approached the asymptote by postnatal day 70 [Oishi T, Higo N, Umino Y, Matsuda K, Hayashi M (1998) Development of GAP-43 mRNA in the macaque cerebral cortex. Dev Brain Res 109:87-97]. The present findings may indicate that extensive synaptic growth of thalamic neurons continues even after that of cortical neurons has finished. We then performed in situ hybridization to investigate whether the expression level of growth-associated protein-43 mRNA was different among various thalamic nuclei. In the infant thalamus (postnatal days 70-90), moderate to intense expression of growth-associated protein-43 mRNA was detected in all thalamic nuclei. Quantitative analysis in the infant thalamus indicated that the expression levels were different between the nuclear groups that are defined by the origin of their afferents. The expression in the first order nuclei, which receive their primary afferent fibers from ascending pathways [Guillery RW (1995) Anatomical evidence concerning the role of the thalamus in corticocortical communication: a brief review. J Anat 187 (Pt 3):583-592], was significantly higher than that in the higher order nuclei. While moderate expression was also detected in the adult dorsal thalamus, the expression in the first order nuclei was almost the same as that in the higher order nuclei. Thus, the in situ hybridization experiments indicated that the transient postnatal increase in the amount of growth-associated protein-43 mRNA, which was shown by the Northern blot analysis, was mainly attributed to enhanced expression in the first order nuclei during the postnatal period. This may be a molecular basis for environmentally induced modification of thalamocortical synapses.

Northern blot and in situ hybridization analyses for the development of myristoylated alanine-rich c-kinase substrate mRNA in the monkey cerebral cortex

Myristoylated alanine-rich C-kinase substrate (MARCKS) is a major neuron-specific substrate for protein kinase C, and is involved in both neurite outgrowth and synaptic plasticity. Using both Northern blot and in situ hybridization techniques, we investigated whether the expression of MARCKS mRNA in the monkey cerebral neocortex and hippocampus changed during the developmental period. In each of four neocortical areas examined, i.e. the prefrontal area (area FD of [Illinois Monographs in the Medical Sciences (1947) 1]), the temporal association area (TE), the primary somatosensory area (PB), and the primary visual area (OC), the Northern blot analysis showed that the amount of MARCKS mRNA was high during the fetal and early postnatal periods, and decreased sharply between postnatal day 70 and postnatal month 6. The in situ hybridization experiments showed that the expression of MARCKS mRNA was decreased in every layer of neocortical areas at postnatal month 6 or later. In the primary sensory areas (areas PB and OC), the degree of decrease was higher in the supragranular layers (layers II and III) than in the infragranular layers (layers V and VI). In the hippocampus, the developmental change in the amount of MARCKS mRNA was small, but the in situ hybridization revealed a prominent decrease in Ammon's horn in monkeys on postnatal month 8 and later. These findings indicate that region-specific expression of MARCKS mRNA is established around postnatal month 6. We suggest that the extensive expression of MARCKS mRNA is one of the molecular bases of high plasticity in the infant cerebral cortex.

Association of verrucous skin lesions and skin ulcers on the feet in patients with diabetic neuropathy

We report the simultaneous or chronological association of verrucous skin lesions and diabetic ulcers on the feet of three diabetic patients. All three patients had poor diabetic control and were suffering from complications such as neuropathy, retinopathy and nephropathy at the time of presentation. In patient 1, verrucous skin lesions on the feet in diabetic neuropathy (VSLDN) and a diabetic skin ulcer developed simultaneously. In patient 2, VSLDN preceded the development of diabetic ulcers, while in patient 3, diabetic ulcers preceded VSLDN. These associations suggest that VSLDN and diabetic ulcers are closely related in their aetiology and pathogenesis. Strategies for the treatment and prevention of VSLDN should include multiple treatment modalities combined with foot care as proposed by the international working group on the diabetic foot.

Iontophoretic pulsatile transdermal delivery of human parathyroid hormone (1-34)

Iontophoretic pulsatile transdermal delivery of hPTH(1-34) was examined in Sprague-Dawley (SD) rats, hairless rats and beagle dogs. Application for 60 min (200 microg; 0.1 mA cm(-2)) showed current-responsive increases in serum hPTH(1-34) levels in all the animals. In SD rats, the area under the curves of serum hPTH(1-34) levels (AUCs) were proportional to the doses (40, 120, 200, 400 and 1000 microg) and current densities (0.05, 0.1 and 0.15mA cm(-2)) applied. The absorption rates per 200-microg dose, calculated by a deconvolution method, were 6.7, 2.4 and 3.7 microg h(-1) for SD rats, hairless rats and beagle dogs, respectively. These values correlated well with the ratios of the skin porosity to the dermal thickness reported for these animals, which are believed to represent the reciprocal of the electrical resistance of the aqueous channels formed by the hair follicles. From this correlation, we suggested that absorption of hPTH(1-34) occurs mainly via the hair-follicle route, and that the absorption rate in man might be intermediate between those in hairless rats and beagle dogs. Three-fold repetitions of 30 min current with various rest intervals produced current-responsive triple pulses in serum hPTH(1-34) levels in SD rats. Seven-fold repetitions of current also produced similar current-responsive pulsatile serum hPTH(1-34) levels. However, peak serum hPTH(1-34) levels tended to decrease gradually after the fourth current application, possibly due to consumption of the electrodes, suggesting that three-fold repetitions of current might be optimal. These findings suggest that this iontophoretic administration system could create a repeated-pulsatile pattern of serum hPTH(1-34) levels without the necessity for frequent injections, and may be useful for the treatment of osteoporosis with hPTH(1-34).

Transdermal administration of salmon calcitonin by pulse depolarization-iontophoresis in rats

Using the pulse depolarization-iontophoresis (PDP-IP) system, salmon calcitonin (sCT), a drug for the treatment of osteoporosis, was transdermaly administered in rats. While absorption of sCT was not observed after passive transdermal administration, the serum sCT concentration was confirmed at a dose of 0.2-4 microg when the PDP-IP system was employed. The results indicated that PDP-IP could enhance transdermal absorption of peptide drugs. Also noted was the increased amount of absorption of sCT along with an increase in the dose. We investigated the influence of electrical parameters (current, frequency) in PDP-IP on the transdermal absorption of sCT. An optimal current for drug absorption was found within the range of transported current (0.1-1.0 mA) employed for PDP-IP. In comparison with the results obtained at 0.1 mA, the drug absorption increased, along with an increase in transported current, when the current was set at 0.5 mA, while the drug absorption decreased at 1.0 mA in comparison. The decrease in drug absorption was assumed to be attributable to the structural destruction of skin by application of excessive current. There was no change in skin resistance attributable to the frequency; nor was there any influence of the frequency on the amount of drug absorption.

Expression of GAP-43 and SCG10 mRNAs in lateral geniculate nucleus of normal and monocularly deprived macaque monkeys

We performed nonradioactive in situ hybridization histochemistry (ISH) in the lateral geniculate nucleus (LGN) of the macaque monkey to investigate the distribution of mRNA for two growth-associated proteins, GAP-43 and SCG10. GAP-43 and SCG10 mRNAs were coexpressed in most neurons of both magnocellular layers (layers I and II) and parvocellular layers (layers III-VI). Double-labeling using nonradioactive ISH and immunofluorescence revealed that both GAP-43 and SCG10 mRNAs were coexpressed with the alpha-subunit of type II calcium/calmodulin-dependent protein kinase, indicating that both mRNAs are expressed also in koniocellular neurons in the LGN. We also showed that GABA-immunoreactive neurons in the LGN did not contain GAP-43 and SCG10 mRNAs, indicating that neither GAP-43 nor SCG10 mRNAs were expressed in inhibitory interneurons in the LGN. GABA-immunoreactive neurons in the perigeniculate nucleus, however, contained both GAP-43 and SCG10 mRNAs, indicating that both mRNAs were expressed in inhibitory neurons in the perigeniculate nucleus, which project to relay neurons in the LGN. Furthermore, to determine whether the expression of GAP-43 and SCG10 mRNAs is regulated by visual input, we performed nonradioactive ISH in the LGN and the primary visual area of monkeys deprived of monocular visual input by intraocular injections of tetrodotoxin. Both mRNAs were downregulated in the LGN after monocular deprivation for 5 d or longer. From these results, we conclude that both GAP-43 and SCG10 mRNAs are expressed in the excitatory relay neurons of the monkey LGN in an activity-dependent manner.

Quantitative non-radioactive in situ hybridization study of GAP-43 and SCG10 mRNAs in the cerebral cortex of adult and infant macaque monkeys

We performed non-radioactive in situ hybridization histochemistry in several areas that include both the association areas and the lower sensory areas of monkey cerebral cortex, and investigated the localization of neurons expressing two growth-associated proteins: GAP-43 and SCG10. Both GAP-43 and SCG10 mRNAs were observed in both pyramidal and non-pyramidal neurons. Prominent hybridization signals for GAP-43 mRNA were observed in layers II-VI of the adult association areas: the prefrontal areas (FD), the temporal (TE) and the parietal (PG) association areas. The signals for GAP-43 mRNA were weak in layers I-III of the adult primary somatosensory area (PB) and primary (OC) and secondary (OB) visual areas, and cells with prominent signals were observed in layers IV-VI. The prominent signals for SCG10 mRNA were observed in layers IV-VI of all areas examined. These results suggest that the expression pattern of GAP-43 mRNA, but not that of SCG10 mRNA, may be related to the functional difference between association and lower sensory areas of adult cortex. In the infant cortex (postnatal days 2, 8 and 31), the signals for both mRNAs were intense in layers II-VI of all areas. Therefore, layer-specific expressions of GAP-43 and SCG10 mRNAs are established after the first postnatal month.

Gene expression of growth-associated proteins, GAP-43 and SCG10, in the hippocampal formation of the macaque monkey: nonradioactive in situ hybridization study

We performed nonradioactive in situ hybridization histochemistry in the monkey hippocampal formation that includes the hippocampus, the subicular complex, and the entorhinal cortex to detect the expression of mRNA for two growth-associated proteins: GAP-43 and SCG10. Overall, the distribution patterns overlapped but were partially distinct. In the hippocampus, the intense hybridization signals for both GAP-43 and SCG10 mRNAs were observed in the pyramidal cell layer of Ammon's horn, especially in CA3 subfields. The intense hybridization signals were also observed in the stratum oriens of Ammon's horn and the polymorphic layer of the dentate gyrus. In the granule cell layer of the dentate gyrus, many GAP-43 mRNA-positive cells were observed, whereas a few positive cells with weak signals were observed for SCG10 mRNA. Throughout the subicular complex, the hybridization signals for both mRNAs were weak. In the entorhinal cortex, both mRNAs were abundant in the caudal field. These subregion-specific expression of the growth-associated proteins may reflect the functional specialization regarding plasticity in each region of the monkey hippocampal formation.

Development of GAP-43 mRNA in the macaque cerebral cortex

To estimate the extent of axonal growth in various areas of the cerebral cortex, we measured the amount of GAP-43 mRNA in the cerebral cortex of developing macaque monkeys. In four areas, i.e., the prefrontal area (FD delta), the temporal association area (TE), the primary somatosensory area (PC), and the primary visual area (OC), the amount of GAP-43 mRNA was measured from the intermediate fetal period [embryonic day 120 (E120)] to the adult stage. In two other areas, i.e., the parietal association area (PG) and the secondary visual area (OB), the amount of GAP-43 mRNA was measured during the postnatal period. The amount of GAP-43 mRNA was highest at E120, decreased roughly exponentially, and approached the asymptote by postnatal day 70 (P70). The amount of GAP-43 mRNA was higher in the association areas (FD delta, TE, and PG) than in the primary sensory areas (PC and OC) during development and at the adult stage. These findings suggest that axonal growth in the cerebral cortex is most exuberant before or during the intermediate fetal period and approximately ends by P70. Furthermore, axonal growth is evidently more intensive in the association areas than in the primary sensory areas during the stage following the intermediate fetal period.

Patch test materials for mercury allergic contact dermatitis

The objective of this study was to define adequate patch test materials to evaluate mercury allergic contact dermatitis. We applied 0.1% and 0.05% mercuric chloride, and 0.5% and 0.2% mercury in petrolatum to systemic eczematous contact-type dermatitis (baboon syndrome), and gold-dermatitis patients. All baboon-syndrome patients reacted not only to mercuric chloride but also to metallic mercury. In gold-dermatitis patients, significantly more patients reacted to mercuric chloride than to metallic mercury (21 of 35, 60%, versus 2 of 19, 10.5%, p < 0.0005). We speculated that sensitization to mercury may be of 2 types: one a reaction to ionized mercury only, the other to both ionized mercury and non-ionized mercury. The possibility that the phenomenon is caused by differences in bioavailability or percutaneous penetration between ionized and non-ionized mercury cannot be ruled out, but could be explored by penetration measurement. For the evaluation of mercury hypersensitivity, it may be more reliable to apply both ionized and non-ionized mercury, rather than only mercuric chloride or ammoniated mercury.

Validation of reflectance infrared spectroscopy as a quantitative method to measure percutaneous absorption in vivo

Attenuated total-reflectance infrared (ATR-IR) spectroscopy has been used to follow the penetration of a model compound (4-cyanophenol; CP) across human stratum corneum (SC) in vivo, in man. CP was administered for periods of 1, 2, or 3 hr, either (a) as a 10% (w/v) solution in propylene glycol or (b) in an identical vehicle which also contained 5% (v/v) oleic (cis-9-octadecenoic) acid. At the end of the treatment periods, SC at the application site was progressively removed by adhesive tape-stripping. Prior to the removal of the first tape-strip, and after each subsequent tape-strip, an ATR-IR spectrum of the treated site was recorded. The presence of CP, as a function of position in the SC, was monitored spectroscopically via the intense C = N stretching absorbance at 2230 cm-1. The absolute amount of CP, as a function of SC depth, was determined by "spiking" the applied solutions with 14C-labeled compound and subsequent liquid scintillation counting of the removed tape-strips. The presence of oleic acid in the applied formulation significantly increased the rate and extent of CP delivery as evaluated by either spectroscopy or radiochemical analysis. Furthermore, the ATR-IR and direct 14C analysis of CP as a function of SC position were highly correlated. These data strongly support, therefore, the validation of ATR-IR as a quantitative tool to assess percutaneous penetration in vivo.

Further evaluation of a new penetration enhancer, HPE-101

The penetration enhancer, 1-[2-(decylthio)ethyl]azacyclopentan-2-one (HPE-101), significantly enhanced the excretion of topically applied [14C]indomethacin when dissolved in dipropylene glycol, triethylene glycol, diethylene glycol, 1,3-butylene glycol, trimethylene glycol, glycerin, water, silicone or triethanolamine, but not when dissolved in ethanol, isopropyl alcohol, oleyl alcohol, olive oil, peppermint oil, isopropyl myristate or hexylene glycol. HPE-101 significantly enhanced the excrection of [14C]indomethacin, [14C]nicotinic acid, [14C]5-fluorouracil, [3H]oestradiol and [3H]triamcinolone acetonide, but not that of [3H]testosterone. HPE-101 also significantly enhanced the excretion of [14C]indomethacin applied to intact skin of rabbit, guinea-pig and rat, and to tape-stripped skin of guinea-pig, but did not enhance the excretion of [14C]indomethacin applied to tape-stripped skin of rat or rabbit.

Evaluation of a new penetration enhancer 1-[2-(decylthio)ethyl]azacyclopentan-2-one (HPE-101)

A new compound, 1-[2-(decylthio)ethyl]azacyclopentan-2-one (HPE-101) was synthesized, and its skin penetration enhancing activity was examined by using 14C-indomethacin as a penetrant. A solution of HPE-101 and indomethacin was applied to a cloth pad affixed onto an adhesive tape to give a HPE-101 patch, and the patch was applied to hairless mouse skin. The amount of percutaneously absorbed indomethacin was determined by measuring the radioactivity excreted in urine for 24 h after application. 1) Azone and decylmethyl sulfoxide, enhanced markedly the percutaneous absorption of indomethacin when the propylene glycol-ethanol (9:1 v/v) mixture was used as the solvent. 2) Among various penetration enhancers dissolved in the indomethacin solutions and applied to screen for penetration enhancing activity, HPE-101 was found to be the most prominent. 3) Solvents containing more than 3% (w/w) of HPE-101 produced a plateau level of the penetration enhancing activity. 4) Daily application of 1% (w/w) solutions of HPE-101 or Azone increased the daily excretion of indomethacin significantly above the level excreted on the previous day. However, repeated daily application beyond 3 d gave a steady state excretion of indomethacin. 5) The mouse skin was pretreated with 3% (w/w) solutions of HPE-101 or Azone for 24 h on the 1st day, and the indomethacin solution was applied for 24 h on the 3rd day and 7th day to examine the recovery of skin barrier function. Enhanced excretion of indomethacin was still noted on the 3rd day, but enhancement was not observed on the 7th day.

Cutaneous metabolism of nitroglycerin in vitro. II. Effects of skin condition and penetration enhancement

The effects of skin storage, skin preparation, skin pretreatment with a penetration enhancer, and skin barrier removal by adhesive tape-stripping on the concurrent cutaneous transport and metabolism of nitroglycerin (GTN) have been studied in vitro using hairless mouse skin. Storing the skin for 10 days at 4 degrees C did not alter barrier function to total nitrate flux [GTN + 1,2-glyceryl dinitrate (1,2-GDN) + 1,3-glyceryl dinitrate (1,3-GDN)]. However, metabolic function was significantly impaired and suggested at least fivefold loss of enzyme activity. Heating skin to 100 degrees C for 5 min appreciably damaged hairless mouse skin barrier function. The ability to hydrolyze GTN was still present, however, and remained constant over the 10-hr experimental period, in contrast to the "control," which showed progressively decreasing enzymatic function with time. Pretreatment of hairless mouse skin in vivo (prior to animal sacrifice, tissue excision, and in vitro transport/metabolism studies) with 1-dodecylazacycloheptan-2-one (Azone), a putative penetration enhancer, significantly lowered the skin barrier to nitrate flux (relative to the appropriate control). Again, barrier perturbation resulted in essentially constant metabolic activity over the observation period. The ratio of metabolites formed (1,2-GDN/1,3-GDN) was increased from less than unity to slightly above 1 by the Azone treatment. Adhesive tape-stripping gradually destroyed skin barrier function by removal of the stratum corneum. The effects of 15 tape-strips were identical to those of Azone pretreatment: a greatly enhanced flux, a constant percentage formation of metabolites over 10 hr (once again), and an increase in the 1,2-GDN/1,3 GDN ratio.(ABSTRACT TRUNCATED AT 250 WORDS)

Cutaneous metabolism of nitroglycerin in vitro. I. Homogenized versus intact skin

The metabolism of nitroglycerin (GTN) to 1,2- and 1,3-glyceryl dinitrate (GDN) by hairless mouse skin in vitro has been measured. In the first set of experiments, GTN was incubated with the 9000g supernatant of fresh, homogenized tissue in the presence and absence of glutathione (GSH), a cofactor for glutathione-S-transferase. After 2 hr of incubation with GSH, 30% of the initially present GTN had been converted to 1,2- and 1,3-GDN; without GSH, less than 5% of the GTN was metabolized. The ratio of 1,2-GDN to 1,3-GDN produced by the homogenate was 1.8-2.1. In the second series of studies, GTN was administered topically to freshly excised, intact hairless mouse skin in conventional in vitro diffusion cells. The concurrent transport and metabolism of GTN was then monitored by sequential analysis of the receptor phase perfusing the dermal side of the tissue. Three topical formulations were used: a low concentration (1 mg/ml) aqueous solution, a 2% ointment, and a transdermal delivery system. Delivery of total nitrates (GTN + 1,2-GDN + 1,3-GDN) into the receptor phase was similar for ointment and patch formulations and much greater than that from the solution. The percentage metabolites formed, however, was greatest for the solution (61% and 2 hr, compared to 49% for the patch and 35% for the ointment). As has been noted before, therefore, the relative level of skin metabolism is likely to be greatest when the transepidermal flux is small. Distinct from the homogenate experiments, the 1,2/1,3-GDN ratios in the penetration studies were in the range 0.7-0.9.(ABSTRACT TRUNCATED AT 250 WORDS)

Percutaneous penetration kinetics of nitroglycerin and its dinitrate metabolites across hairless mouse skin in vitro

The percutaneous penetration kinetics of the antianginal, nitroglycerin (GTN), and its primary metabolites, 1,2- and 1,3-glyceryl dinitrate (1,2- and 1,3-GDN), were evaluated in vitro, using full-thickness hairless mouse skin. GTN and the 1,2- and 1,3-GDNs were applied (a) in aqueous solution as pH 7.4 phosphate-buffered saline (PBS) and (b) incorporated into lipophilic ointment formulations. The cutaneous transformation of GTN to its dinitrate metabolites was detected, but no interconversion between 1,2-GDN and 1,3-GDN was observed. Following application of the nitrates in PBS solution, all three compounds exhibited steady-state transport kinetics. The steady-state flux of GTN (8.9 +/- 1.5 nmol cm-2 hr-1) was significantly greater (P less than 0.05) than those of 1,2-GDN (0.81 +/- 0.54 nmol cm-2 hr-1) and 1,3-GDN (0.72 +/- 0.20 nmol cm-2 hr-1). The corresponding permeability coefficient (rho) for GTN (20 +/- 3 x 10(-3) cm hr-1) was significantly larger than the corresponding values for 1,2-GDN (1.4 +/- 0.9 x 10(-3) cm hr-1) and 1,3-GDN (1.2 +/- 0.4 x 10(-3) cm hr-1), which were statistically indistinguishable (P greater than 0.05). Further analysis of the transport data showed that the differences between GTN and the GDNs could be explained by the relative stratum corneum/water partition coefficient (Ks) values of the compounds. The apparent partition parameters, defined as kappa = Ks.h [where h is the diffusion path length through stratum corneum (SC)] were 19.8 +/- 2.5 x 10(-2) cm for GTN and 1.91 +/- 1.07 x 10(-2) and 1.81 +/- 0.91 x 10(-2) cm for 1,2- and 1,3-GDN, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)